Newton's Laws Warm Up

Think about a time you pushed something, or something pushed you! Write down what happened.

1. Describe a situation where you pushed or pulled an object. What happened to the object? Did it start moving, stop moving, or change direction?





2. If you throw a ball, what makes it stop? If it keeps moving, what keeps it going?





3. When you jump, what pushes you up? What pushes the Earth down?

Unlocking the Universe: Newton's Three Laws of Motion

Have you ever wondered why things move the way they do? Why does a ball stop rolling? Why is it harder to push a heavy box than a light one? And what happens when you push on something – does it push back? For centuries, humans pondered these questions until a brilliant scientist named Isaac Newton came along and gave us the answers. His three laws of motion are like the instruction manual for how everything moves in our universe.

Newton's First Law: The Law of Inertia (An Object in Motion Stays in Motion... Unless!)

Imagine you're on a skateboard rolling down a smooth, flat sidewalk. What would happen if nothing stopped you? You'd keep rolling forever, right? That's the essence of Newton's First Law! It states:

An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

This law is also known as the Law of Inertia. Inertia is a property of matter that resists changes in motion. The more mass an object has, the more inertia it has, and the harder it is to get it moving or to stop it once it's moving.

• At Rest: A book sitting on a table won't suddenly fly off. It stays at rest because there's no unbalanced force pushing or pulling it.
• In Motion: If you slide a puck across ice, it travels a long way before friction (an outside force) eventually stops it. In space, an object set in motion would literally keep going forever!

Think about it: When a car suddenly stops, your body lurches forward. Why? Because your body, which was in motion with the car, wants to continue in motion due to inertia!

Newton's Second Law: The Force Equation (F=ma)

What if you do want to change an object's motion? How much force do you need? Newton's Second Law gives us the answer with a famous equation:

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This is often written as: F = ma

Where:

• F stands for Force (measured in Newtons, N)
• m stands for mass (measured in kilograms, kg)
• a stands for acceleration (measured in meters per second squared, m/s²)

This law tells us a few important things:

• More Force, More Acceleration: If you push a small toy car gently, it speeds up slowly. If you push it hard, it speeds up quickly. More force means more acceleration.
• More Mass, Less Acceleration: If you push a shopping cart with the same force you pushed the toy car, the shopping cart will accelerate much less. More mass means less acceleration (for the same amount of force).

Example: If you apply a force of 10 Newtons to a 2 kg object, its acceleration will be:
a = F / m = 10 N / 2 kg = 5 m/s²

This law is incredibly powerful because it allows us to calculate exactly how forces will affect the motion of objects.

Newton's Third Law: The Law of Action and Reaction (Every Push Has a Push Back!)

Have you ever wondered how a rocket takes off? It pushes gas downwards, and the gas pushes the rocket upwards! This is Newton's Third Law in action:

For every action, there is an equal and opposite reaction.

This means that forces always come in pairs. When one object exerts a force on a second object, the second object simultaneously exerts a force equal in magnitude and opposite in direction on the first object.

• Walking: When you walk, your foot pushes backward on the ground (action). The ground pushes forward on your foot (reaction), propelling you forward.
• Swimming: A swimmer pushes water backward (action), and the water pushes the swimmer forward (reaction).
• Rocket Launch: The rocket engines push hot gas downwards (action). The hot gas pushes the rocket upwards (reaction).

It's important to remember that these action and reaction forces act on different objects. The foot pushes the ground, and the ground pushes the foot. They don't cancel each other out because they aren't acting on the same object. They are always equal in strength and opposite in direction.

Newton's Three Laws of Motion are fundamental to understanding the physical world. From the simple act of kicking a ball to the complex orbits of planets, these laws provide the framework for explaining all motion.

Newton's Laws Script

Session 1: Introduction to Newton's First Law

Warm Up Discussion (10 minutes)

Teacher: "Good morning, everyone! Let's start with our warm-up. Take a few minutes to think about the questions on the Newton's Laws Warm Up and jot down your thoughts. Don't worry about perfect answers, just what comes to mind."

(Allow students to work for 5-7 minutes. Then facilitate a brief discussion.)

Teacher: "Alright, who would like to share their response to question 1? Describe a situation where you pushed or pulled an object. What happened?"

Teacher: "Excellent! And what about question 2? If you throw a ball, what makes it stop? If it keeps moving, what keeps it going?"

Teacher: "Great responses. Keep these ideas in mind as we dive into today's topic."

Introduction to Newton's First Law (15 minutes)

(Display Slide: "Laws of Motion Mania!")

Teacher: "Today, we're going to start unlocking some of the biggest mysteries in our universe: Why do things move the way they do? Why does a rolling ball eventually stop? Why is it much harder to push a heavy box than a light one? And when you push something, does it push back? These are questions that have fascinated thinkers for centuries, and today, we're going to explore the answers given to us by one of the most brilliant minds in history."

(Display Slide: "Meet Sir Isaac Newton")

Teacher: "That's right, we're talking about Sir Isaac Newton. He wasn't just a physicist; he was also a mathematician, astronomer, theologian, and author. He developed the three fundamental laws of motion that we still use today to explain everything from a simple push to the complex orbits of planets. These laws are truly the instruction manual for how our universe moves."

(Display Slide: "Newton's First Law: The Law of Inertia")

Teacher: "Let's start with his First Law, often called the Law of Inertia. It states: 'An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.' In simpler terms, things are kind of 'lazy.' If something isn't moving, it wants to stay put. If something is moving, it wants to keep moving exactly as it is, forever, unless something interferes."

Teacher: "The key phrase here is 'unbalanced force.' Can anyone give me an idea of what an unbalanced force might be?"

Teacher: "Exactly! It's a force that isn't canceled out by other forces, so it causes a change. Think about a tug-of-war where one team pulls harder than the other – that's an unbalanced force. We'll explore this more later."

(Display Slide: "Inertia in Action!")

Teacher: "Let's look at some examples of inertia. A book sitting on a table. Does it move on its own? No, it stays at rest because there are no unbalanced forces acting on it. If I slide a hockey puck across a really smooth surface, like ice, it goes a long way, right? That's because friction, the force trying to stop it, is very small. In space, if you threw something, it would literally keep going forever because there's almost no friction or air resistance to stop it."

Teacher: "And my favorite example: when you're riding in a car and the driver suddenly hits the brakes, what happens to you?"

Teacher: "You lurch forward! That's your body's inertia. Your body was in motion with the car and it wants to stay in motion, even when the car stops."

Reading & Discussion (20 minutes)

Teacher: "Now, I'm going to hand out the Newton's Laws Reading. Please read the section that talks about Newton's First Law, 'The Law of Inertia.' You can read it silently to yourselves or with a partner. As you read, think about any questions you have or connections you can make."

(Distribute reading. Allow 10-12 minutes for reading.)

Teacher: "Let's discuss. What was one new thing you learned or found interesting about the Law of Inertia from the reading?"

Teacher: "Why do you think it's important to wear a seatbelt, based on Newton's First Law?"

Demonstrations (15 minutes)

Teacher: "Let's see inertia in action with a few demonstrations."

(Perform the following demonstrations, explaining the physics as you go:)

• Tablecloth Trick: "I have some objects on a tablecloth. If I pull the tablecloth out quickly, what do you think will happen to the objects? Why?" (Perform. Explain that the objects' inertia resists the sudden change in motion.)
• Coin Drop: "I have a card on top of a glass with a coin on the card. If I flick the card, what happens to the coin?" (Perform. Explain the coin's inertia keeps it at rest until gravity pulls it down into the glass when the card is removed.)
• Toy Car and Wall: "Here's a toy car. If I roll it and it hits a wall, what happens to the car? What about a small figure inside the car?" (Perform. Explain the car stops, but the figure continues forward due to inertia.)

Teacher: "Any final questions about Newton's First Law and inertia before we wrap up for today?"

Session 2: Newton's Second Law - F=ma

Review (10 minutes)

Teacher: "Welcome back! To quickly recap from last time, who can remind us what Newton's First Law, the Law of Inertia, is all about?"

Teacher: "Excellent! And what's that key phrase about a force that causes a change in motion?"

Teacher: "Spot on! An unbalanced force. Today, we're going to dive deeper into what happens when there is an unbalanced force."

Introduction to F=ma (20 minutes)

(Display Slide: "Newton's Second Law: Force = Mass x Acceleration")

Teacher: "Newton's Second Law is where things get really exciting, and we get a powerful equation that helps us understand how much things change when an unbalanced force acts on them. This law explains the relationship between force, mass, and acceleration."

(Display Slide: "The Famous Formula: F = ma")

Teacher: "The law is summarized by this famous equation: F = ma. Let's break down what each part means."

• F is for Force. "Force is a push or a pull. We measure force in a unit called Newtons, abbreviated with a capital 'N'. A Newton is actually a combination of other units, but for now, just remember 'N'."
• m is for mass. "Mass is the amount of 'stuff' in an object. It's a measure of its inertia. We measure mass in kilograms, 'kg'. Remember, mass is not the same as weight! Weight is a force due to gravity, while mass is an intrinsic property of an object."
• a is for acceleration. "Acceleration is the rate at which an object's velocity changes. It means speeding up, slowing down, or changing direction. We measure acceleration in meters per second squared, 'm/s²'."

Teacher: "So, F = ma tells us that if you apply a force (F) to an object with a certain mass (m), it will accelerate (a). And the key takeaways are: more force means more acceleration, and for the same force, more mass means less acceleration. Does that make intuitive sense? If you push a small car and a big truck with the same amount of effort, which one speeds up more?"

Teacher: "The small car, right? Less mass, more acceleration for the same force."

Guided Practice (20 minutes)

(Display Slide: "Let's Practice F=ma!")

Teacher: "Let's try an example problem together. A net force of 20 N is applied to a 5 kg object. What is its acceleration?"

Teacher: "First, what do we know? What are our 'givens'?"

Teacher: "Right, Force = 20 N and Mass = 5 kg. What are we trying to find?"

Teacher: "Acceleration. Now, what's our formula?"

Teacher: "F = ma. We need to rearrange it to solve for 'a', so a = F/m. Now, plug in the numbers and solve!" (Guide students through the calculation.)

Teacher: "So, the acceleration is 4 m/s². Remember to always include your units!"

(Display Slide: "Your Turn! F=ma")

Teacher: "Alright, your turn! What force is needed to accelerate a 10 kg object at 3 m/s²? Take a minute to work this out on your own or with a neighbor." (Allow time for students to work, then call on someone to share their steps and answer.)

Teacher: "Excellent! The force needed is 30 N. You're doing great with F=ma!"

Independent Practice (10 minutes)

Teacher: "Now, I'm going to hand out the Newton's Laws Worksheet. Please work on the problems that focus on F=ma. We will go over these next time, and you can finish any remaining problems for homework. Feel free to ask questions if you get stuck."

(Distribute worksheet and circulate to assist students.)

Session 3: Newton's Third Law - Action-Reaction

Review and Warm-up (15 minutes)

Teacher: "Welcome back! Last time, we introduced Newton's Second Law, F=ma. Who can tell me what F=ma allows us to calculate?"

Teacher: "Great! And what are the units for Force, Mass, and Acceleration?"

Teacher: "Fantastic! I've also put some problems on the board from the Newton's Laws Worksheet for you to check your work. (Quickly review the F=ma problems from the worksheet, using the Newton's Laws Answer Key as reference.) Any questions on these?"

Teacher: "To transition to today's topic, imagine I have a soccer ball and I kick it. I apply a force to the ball, and it accelerates. That's our Second Law. But what else is happening in that interaction? Is the ball doing anything to my foot?"

Introduction to Third Law (20 minutes)

(Display Slide: "Newton's Third Law: Action-Reaction Pairs")

Teacher: "That leads us perfectly into Newton's Third Law, which is sometimes the trickiest to understand, but it's also really fascinating. It states: 'For every action, there is an equal and opposite reaction.'"

Teacher: "This means that forces never happen alone. They always come in pairs. When one object exerts a force on a second object (the 'action'), the second object simultaneously exerts a force equal in magnitude and opposite in direction on the first object (the 'reaction'). It's like a scientific handshake!"

Teacher: "The most important thing to remember here is that these action and reaction forces act on different objects. The foot pushes the ground, and the ground pushes the foot. They don't cancel each other out because they aren't acting on the same object. They are always equal in strength and opposite in direction."

Teacher: "Think about pushing against a wall. What do you feel?"

Teacher: "You feel the wall pushing back! If you push harder, the wall pushes back harder. If you push softer, it pushes back softer. It's an equal and opposite reaction."

(Display Slide: "Third Law Examples!")

Teacher: "Let's look at more examples. When you walk, your foot pushes backward on the ground – that's the action. What's the reaction?"

Teacher: "Right, the ground pushes forward on your foot, propelling you forward! What about a rocket launching? What's the action and reaction there?"

Teacher: "Excellent! The rocket pushes hot gas downwards (action), and the gas pushes the rocket upwards (reaction), making it launch into space. This is how planes fly, how cars move, how everything moves!"

Action-Reaction Exploration (25 minutes)

Teacher: "Now, it's your turn to identify some action-reaction pairs! We're going to do the Newton's Laws Activity: Force Frenzy Challenge. I'll divide you into small groups. Each group will get a scenario, and your task is to identify the action force and the reaction force. Remember, they act on different objects! Be ready to share your findings with the class."

(Divide students into groups, distribute the activity instructions, and circulate to provide support and answer questions.)

Session 4: Applying All Three Laws

Activity Debrief (15 minutes)

Teacher: "Let's debrief our Newton's Laws Activity: Force Frenzy Challenge. Who would like to share their scenario and the action-reaction pair you identified? Let's make sure we're all clear on this important concept." (Have each group present their findings and facilitate a brief discussion for each scenario, correcting any misconceptions.)

Teacher: "Fantastic work identifying those pairs! The key takeaway is always: forces come in pairs, and they act on different objects."

Worksheet Completion (25 minutes)

Teacher: "Now that we've covered all three laws, let's revisit our Newton's Laws Worksheet. Please complete the remaining problems that involve distinguishing between the laws and applying all three concepts. You can work independently or with a partner. I'll be circulating to answer any questions you have." (Distribute worksheet if not already distributed, or have students retrieve it. Circulate and assist.)

Introduction to Project (20 minutes)

Teacher: "For our final activity in this unit, we're going to put all your understanding of Newton's Laws into a creative project! We'll be working on the Newton's Laws Project: Rube Goldberg Machine. Has anyone heard of a Rube Goldberg machine before?"

Teacher: "A Rube Goldberg machine is a contraption that is intentionally designed to perform a simple task in an overly complicated fashion, using a chain reaction. Your challenge will be to design and conceptualize (you won't build a physical one, just design it) a Rube Goldberg machine that demonstrates at least two of Newton's Laws of Motion."

Teacher: "You'll need to clearly identify how each part of your machine showcases a law. For example, a ball rolling down a ramp might show inertia, or a domino falling might show action-reaction. You'll create a diagram and write a short explanation."

Teacher: "Take a look at the Rube Goldberg Project Rubric. This explains exactly what I'll be looking for in your designs and explanations. We'll have time to work on this next session, but feel free to start brainstorming now or ask any initial questions."

(Distribute project guide and rubric, answer questions.)

Session 5: Project Work and Wrap-up

Project Work Session (45 minutes)

Teacher: "Today is a dedicated work session for your Newton's Laws Project: Rube Goldberg Machine. Use this time wisely to develop your ideas, sketch your diagrams, and write your explanations. Remember to clearly identify how your machine demonstrates Newton's Laws, as outlined in the Rube Goldberg Project Rubric. I'll be walking around to help, answer questions, and provide feedback."

(Circulate, offer guidance, and check for understanding of how laws are being applied.)

Cool Down (15 minutes)

Teacher: "Alright everyone, please wrap up your project work for now. We'll finish with our Newton's Laws Cool Down. This is your chance to reflect on everything we've learned about Newton's Laws. Please answer the questions thoughtfully and turn them in as you leave. Your responses will help me see what stuck with you the most!"

(Distribute cool down, collect responses as students leave.)

Teacher: "Thank you all for an engaging unit on Newton's Laws! I hope you now see the world of motion in a whole new way."

Newton's Laws of Motion: Practice Worksheet

Part 1: Newton's First Law - Law of Inertia

1. Define Newton's First Law in your own words.
   
   
   
   
2. What is inertia? How does the mass of an object relate to its inertia?
   
   
   
   
3. Imagine you are in a car that suddenly makes a sharp turn to the left. Which way does your body feel like it's being thrown? Explain why using Newton's First Law.
   
   
   
   
   
   
4. Give two examples from your daily life where Newton's First Law is demonstrated.
   
   
   
   
   
   

Part 2: Newton's Second Law - F=ma

Show all your work, including the formula, substituted values, and units in your final answer.

5. A net force of 50 N is applied to a 10 kg object. What is its acceleration?
   
   
   
   
   
   
   
6. What force is required to accelerate a 2 kg bowling ball at 5 m/s²?
   
   
   
   
   
   
   
7. An object accelerates at 2 m/s² when a net force of 10 N is applied. What is the mass of the object?
   
   
   
   
   
   
   
8. If you push a 0.5 kg toy car with a force of 2 N, what will its acceleration be?
   
   
   
   
   
   
   

Part 3: Newton's Third Law - Action-Reaction

9. State Newton's Third Law in your own words.
   
   
   
   
10. Explain the difference between action-reaction forces and balanced forces. On what do action-reaction forces act?
    
    
    
    
    
    
11. Identify the action and reaction forces in the following scenarios:
    • Scenario A: A bird flies by pushing air downwards.
      Action:
      Reaction:
      
      
    • Scenario B: A swimmer pushes water backward to move forward.
      Action:
      Reaction:
      
      
    • Scenario C: You kick a soccer ball.
      Action:
      Reaction:
      
      
    • Scenario D: A book rests on a table.
      Action:
      Reaction:
      
      

Part 4: Identifying Newton's Laws

For each statement below, identify which of Newton's Three Laws of Motion (First, Second, or Third) it best describes.

12. A car crashes into a wall, and the passenger continues to move forward until hitting the dashboard.
    Law:
    
    

13. A rocket lifts off the launchpad by expelling hot gases downwards.
    Law:
    
    

14. It takes more force to push a loaded shopping cart than an empty one to achieve the same acceleration.
    Law:
    
    

15. A satellite orbits Earth at a constant speed in a circular path (assume no air resistance).
    Law:
    
    

16. When you jump, your feet push on the ground, and the ground pushes back on your feet.
    Law:
    
    

17. A baseball thrown with more force travels faster.
    Law:
    
    

Newton's Laws of Motion: Answer Key

Part 1: Newton's First Law - Law of Inertia

1. Define Newton's First Law in your own words.

   • Thought Process: The First Law is about an object's resistance to change in motion. It's often called inertia. An object won't start moving if it's still, and won't stop/change direction if it's moving, unless something pushes or pulls it unevenly.
   • Answer: An object will maintain its current state of motion (either at rest or moving at a constant velocity) unless an unbalanced force acts upon it.

2. What is inertia? How does the mass of an object relate to its inertia?

   • Thought Process: Recall the definition of inertia from the reading. Remember that mass is the measure of inertia.
   • Answer: Inertia is the natural tendency of an object to resist changes in its state of motion. The more mass an object has, the greater its inertia, meaning it is harder to start moving, stop moving, or change its direction.

3. Imagine you are in a car that suddenly makes a sharp turn to the left. Which way does your body feel like it's being thrown? Explain why using Newton's First Law.

   • Thought Process: Connect the lurching feeling to the idea that your body wants to continue in a straight line. The car turns, but your body resists that change.
   • Answer: Your body feels like it's being thrown to the right. This is due to Newton's First Law (inertia). Your body was initially moving in a straight line (or with the car before the turn) and tries to continue in that straight line, even when the car changes direction. The car turns left around you.

4. Give two examples from your daily life where Newton's First Law is demonstrated.

   • Thought Process: Think about everyday situations where things continue moving or stay still unexpectedly.
   • Answer: (Any two of the following or similar):
     • A soccer ball sitting on the grass doesn't move until it's kicked.
     • When riding a bicycle and you suddenly apply the brakes, your body tends to keep moving forward.
     • Shaking a ketchup bottle to get the ketchup out (the bottle stops, but the ketchup's inertia makes it continue moving).
     • Leaving groceries on the car seat; if you stop suddenly, they slide forward.

Part 2: Newton's Second Law - F=ma

5. A net force of 50 N is applied to a 10 kg object. What is its acceleration?

   • Thought Process: Identify F and m, then rearrange F=ma to a=F/m and calculate.
   • Given: F = 50 N, m = 10 kg
   • Formula: a = F/m
   • Solution: a = 50 N / 10 kg = 5 m/s²

6. What force is required to accelerate a 2 kg bowling ball at 5 m/s²?

   • Thought Process: Identify m and a, then use F=ma to calculate.
   • Given: m = 2 kg, a = 5 m/s²
   • Formula: F = ma
   • Solution: F = (2 kg) * (5 m/s²) = 10 N

7. An object accelerates at 2 m/s² when a net force of 10 N is applied. What is the mass of the object?

   • Thought Process: Identify a and F, then rearrange F=ma to m=F/a and calculate.
   • Given: a = 2 m/s², F = 10 N
   • Formula: m = F/a
   • Solution: m = 10 N / 2 m/s² = 5 kg

8. If you push a 0.5 kg toy car with a force of 2 N, what will its acceleration be?

   • Thought Process: Identify m and F, then rearrange F=ma to a=F/m and calculate.
   • Given: m = 0.5 kg, F = 2 N
   • Formula: a = F/m
   • Solution: a = 2 N / 0.5 kg = 4 m/s²

Part 3: Newton's Third Law - Action-Reaction

9. State Newton's Third Law in your own words.

   • Thought Process: The Third Law is about forces coming in pairs, equal and opposite, acting on different objects.
   • Answer: For every action force, there is an equal and opposite reaction force. These two forces act on different objects.

10. Explain the difference between action-reaction forces and balanced forces. On what do action-reaction forces act?

    • Thought Process: Balanced forces act on the same object and cancel out to zero net force. Action-reaction forces act on different objects and do not cancel out for a single object.
    • Answer: Balanced forces act on the same object and result in no change in motion (zero net force). Action-reaction forces act on different objects and are responsible for motion. Action-reaction forces always act on different objects.

11. Identify the action and reaction forces in the following scenarios:

    • Scenario A: A bird flies by pushing air downwards.
      • Action: Bird pushes air downwards.
      • Reaction: Air pushes bird upwards.
    • Scenario B: A swimmer pushes water backward to move forward.
      • Action: Swimmer pushes water backward.
      • Reaction: Water pushes swimmer forward.
    • Scenario C: You kick a soccer ball.
      • Action: Foot pushes ball forward.
      • Reaction: Ball pushes foot backward.
    • Scenario D: A book rests on a table.
      • Action: Book pushes down on the table.
      • Reaction: Table pushes up on the book.

Part 4: Identifying Newton's Laws

12. A car crashes into a wall, and the passenger continues to move forward until hitting the dashboard.

    • Law: First Law (Inertia)

13. A rocket lifts off the launchpad by expelling hot gases downwards.

    • Law: Third Law (Action-Reaction)

14. It takes more force to push a loaded shopping cart than an empty one to achieve the same acceleration.

    • Law: Second Law (F=ma - more mass requires more force for same acceleration)

15. A satellite orbits Earth at a constant speed in a circular path (assume no air resistance).

    • Law: First Law (maintaining constant speed and direction without an unbalanced force in its tangential motion; the gravitational force is an unbalanced force causing the circular motion, but the question implies the

Newton's Laws Activity: Force Frenzy Challenge

Objective: To correctly identify action and reaction force pairs in various everyday scenarios, demonstrating an understanding of Newton's Third Law of Motion.

Instructions:

1. Work in your assigned small groups.
2. Each group will receive a scenario card (or a scenario will be displayed).
3. As a group, discuss the scenario and identify the action force and the reaction force involved.
4. Remember, action and reaction forces:
   • Are equal in magnitude.
   • Are opposite in direction.
   • Always act on different objects!
5. Be prepared to present your scenario and the identified action-reaction pair to the class, explaining which object is exerting the force and which object is receiving the force for both the action and the reaction.

Scenario Cards (Cut these out or write on board)

Scenario 1: Kicking a Football

When a football player kicks a football, the player's foot exerts a force on the ball, sending it flying.

• Action Force:
  
  
• Reaction Force:
  
  
  
  

Scenario 2: Rowing a Boat

A person in a rowboat pushes the water backward with an oar to move the boat forward.

• Action Force:
  
  
• Reaction Force:
  
  
  
  

Scenario 3: Jumping Upwards

When you jump, your feet push down on the ground, and then you move upwards.

• Action Force:
  
  
• Reaction Force:
  
  
  
  

Scenario 4: A Book on a Shelf

A heavy book is resting silently on a sturdy bookshelf.

• Action Force:
  
  
• Reaction Force:
  
  
  
  

Scenario 5: A Cannon Firing

When a cannon fires, it shoots a cannonball forward out of its barrel.

• Action Force:
  
  
• Reaction Force:
  
  
  
  

Scenario 6: Car Accelerating

The tires of a car push backward on the road to make the car move forward.

• Action Force:
  
  
• Reaction Force:
  
  
  
  

Newton's Laws Project: Rube Goldberg Machine

Objective:

Design a Rube Goldberg machine that demonstrates at least two of Newton's Three Laws of Motion. Your design should clearly label and explain how each chosen law is showcased within your machine's sequence of events.

What is a Rube Goldberg Machine?

A Rube Goldberg machine is a contraption, device, or apparatus that is deliberately over-engineered to perform a simple task in a complicated fashion, generally using a chain reaction. Think of it as a series of dominoes falling, but with more creative and diverse physics at play!

Project Components:

1. Machine Diagram:
   • Create a clear, labeled diagram or drawing of your Rube Goldberg machine.
   • Your diagram should show at least five distinct steps or stages in the chain reaction.
   • Each step should be clearly labeled (e.g.,

Rube Goldberg Project Rubric

Newton's Laws Cool Down

1. In your own words, what is the main idea of Newton's First Law (Law of Inertia)? Give one real-world example.
   
   
   
   
2. Explain Newton's Second Law (F=ma). If you want to make an object accelerate more, what two things could you change?
   
   
   
   
3. Describe Newton's Third Law (Action-Reaction). When you push on a wall, why doesn't the wall move even though it pushes back on you with an equal and opposite force?
   
   
   
   
   
   
4. What was the most interesting or surprising thing you learned about Newton's Laws today? Why?
   
   
   
   

Forces and Free Body Diagrams: Practice Worksheet

Part 1: Identifying and Defining Forces

1. Define the following types of forces in your own words:
   • Net Force:
     
     
     
   • Force of Gravity (Weight):
     
     
     
   • Normal Force:
     
     
     
   • Applied Force:
     
     
     
   • Friction Force:
     
     
     
   • Tension Force:
     
     
     

Part 2: Calculating Forces (Show all work and units!)

Use g = 9.8 m/s² for acceleration due to gravity.

2. A 15 kg object rests on a table. What is the force of gravity acting on it (its weight)?
   
   
   
   
   
   
3. A person applies a 75 N force to push a 20 kg box across a floor. The friction force resisting the motion is 15 N. What is the net force acting on the box?
   
   
   
   
   
   
4. A rope is used to pull a 5 kg bucket straight up with an acceleration of 2 m/s². What is the tension force in the rope? (Hint: Consider gravity and the net force.)
   
   
   
   
   
   
   
   
   
   
   
5. A 50 N force is applied to a 5 kg block horizontally. If the block accelerates at 8 m/s², what is the friction force acting on the block?
   
   
   
   
   
   

Part 3: Drawing Free Body Diagrams

Draw a free body diagram for each scenario. Label all forces with arrows showing direction and appropriate symbols (e.g., Fg, Fn, Fa, Ff, Ft). You do not need to label magnitudes unless specified.

6. A book resting on a flat table.
   
   
   
   
   
   
   
   
   
   
   
   
   

7. A box being pushed horizontally across a rough floor at a constant velocity.
   
   
   
   
   
   
   
   
   
   
   
   
   

8. A car accelerating forward on a level road.
   
   
   
   
   
   
   
   
   
   
   
   
   

9. A person hanging motionless from a rope.
   
   
   
   
   
   
   
   
   
   
   
   
   

Part 4: Analyzing Free Body Diagrams and Net Force

For each free body diagram below, determine the net force (magnitude and direction) acting on the object.

10. 
    Net Force:
    
    

11. 
    Net Force:
    
    

12. 
    Net Force:
    
    

13. 
    Net Force:
    
    

Forces and Free Body Diagrams: Answer Key

Part 1: Identifying and Defining Forces

1. Define the following types of forces in your own words:
   • Net Force:
     • Thought Process: The overall force acting on an object, determining if and how it accelerates. It's the sum of all individual forces.
     • Answer: The sum of all forces acting on an object. It is the unbalanced force that causes an object to accelerate.
   • Force of Gravity (Weight):
     • Thought Process: The force pulling an object towards the center of a celestial body (like Earth). It depends on mass and the acceleration due to gravity.
     • Answer: The attractive force between any two objects with mass, commonly experienced as the pull of Earth on an object, directed downwards. It is calculated as Fg = mg.
   • Normal Force:
     • Thought Process: When an object rests on a surface, the surface pushes back. This push is perpendicular to the surface.
     • Answer: The force exerted by a surface perpendicular to the surface of contact, pushing outwards on an object that is resting on it or in contact with it.
   • Applied Force:
     • Thought Process: Any push or pull actively exerted by a person or another object.
     • Answer: A force that is directly applied to an object by a person or another object.
   • Friction Force:
     • Thought Process: A force that opposes motion between surfaces in contact. It always works against the direction of movement or attempted movement.
     • Answer: A force that opposes the relative motion or tendency of motion between two surfaces in contact. It acts parallel to the surface.
   • Tension Force:
     • Thought Process: The pulling force transmitted through a string, rope, cable, or chain when it is pulled tight by forces acting from opposite ends.
     • Answer: The force transmitted through a rope, string, cable, or similar connector when pulled taut from opposite ends. It acts along the length of the flexible connector.

Part 2: Calculating Forces (Show all work and units!)

Use g = 9.8 m/s² for acceleration due to gravity.

2. A 15 kg object rests on a table. What is the force of gravity acting on it (its weight)?

   • Thought Process: Weight is the force of gravity, calculated by Fg = mg. Plug in the mass and g.
   • Given: m = 15 kg, g = 9.8 m/s²
   • Formula: Fg = mg
   • Solution: Fg = (15 kg) * (9.8 m/s²) = 147 N

3. A person applies a 75 N force to push a 20 kg box across a floor. The friction force resisting the motion is 15 N. What is the net force acting on the box?

   • Thought Process: Net force is the sum of all forces. Applied force is in one direction, friction in the opposite. So, subtract friction from applied force.
   • Given: Fa = 75 N (applied), Ff = 15 N (friction, opposite direction)
   • Formula: Fnet = Fa - Ff (assuming applied is positive direction)
   • Solution: Fnet = 75 N - 15 N = 60 N

4. A rope is used to pull a 5 kg bucket straight up with an acceleration of 2 m/s². What is the tension force in the rope? (Hint: Consider gravity and the net force.)

   • Thought Process: First, find the force of gravity (weight) acting downwards. Then, use Fnet = ma to find the required net upward force for acceleration. Tension (upwards) minus gravity (downwards) equals net force. So, Ft - Fg = Fnet, or Ft = Fnet + Fg.
   • Given: m = 5 kg, a = 2 m/s², g = 9.8 m/s²
   • Step 1: Calculate Force of Gravity (Fg): Fg = mg = (5 kg)(9.8 m/s²) = 49 N (downwards)
   • Step 2: Calculate Net Force (Fnet): Fnet = ma = (5 kg)(2 m/s²) = 10 N (upwards, since bucket accelerates upwards)
   • Step 3: Calculate Tension Force (Ft): Fnet = Ft - Fg => Ft = Fnet + Fg
   • Solution: Ft = 10 N + 49 N = 59 N

5. A 50 N force is applied to a 5 kg block horizontally. If the block accelerates at 8 m/s², what is the friction force acting on the block?

   • Thought Process: First, use Fnet = ma to find the actual net force. Then, knowing the applied force and the net force, find friction. Fa - Ff = Fnet, so Ff = Fa - Fnet.
   • Given: Fa = 50 N, m = 5 kg, a = 8 m/s²
   • Step 1: Calculate Net Force (Fnet): Fnet = ma = (5 kg)(8 m/s²) = 40 N
   • Step 2: Calculate Friction Force (Ff): Fnet = Fa - Ff => Ff = Fa - Fnet
   • Solution: Ff = 50 N - 40 N = 10 N

Part 3: Drawing Free Body Diagrams

(Diagrams should show arrows originating from the center of the object, labeled with force type and correct direction.)

6. A book resting on a flat table.

   • Thought Process: Two forces: gravity downwards, normal force upwards. They are equal and opposite, resulting in zero net force.
   • Diagram:
     • Arrow pointing down, labeled Fg (or Weight)
     • Arrow pointing up from surface, labeled Fn (or Normal)

7. A box being pushed horizontally across a rough floor at a constant velocity.

   • Thought Process: If constant velocity, net force is zero. So, horizontal forces (applied and friction) must be equal and opposite. Vertical forces (gravity and normal) are also equal and opposite.
   • Diagram:
     • Arrow pointing down, labeled Fg
     • Arrow pointing up, labeled Fn (equal to Fg)
     • Arrow pointing in direction of push, labeled Fa (Applied)
     • Arrow pointing opposite to push, labeled Ff (Friction) (equal to Fa)

8. A car accelerating forward on a level road.

   • Thought Process: Accelerating forward means there's a net force forward. The forward applied force (engine/traction) must be greater than friction. Vertical forces are balanced.
   • Diagram:
     • Arrow pointing down, labeled Fg
     • Arrow pointing up, labeled Fn (equal to Fg)
     • Longer arrow pointing forward, labeled Fa (Applied/Traction)
     • Shorter arrow pointing backward, labeled Ff (Friction)

9. A person hanging motionless from a rope.

   • Thought Process: Motionless means net force is zero. Two forces: gravity downwards, tension upwards. They are equal and opposite.
   • Diagram:
     • Arrow pointing down, labeled Fg
     • Arrow pointing up, labeled Ft (Tension) (equal to Fg)

Part 4: Analyzing Free Body Diagrams and Net Force

10. 

    • Thought Process: Forces are in opposite directions, so subtract them. 15N - 10N = 5N. The larger force is to the right, so the net force is to the right.
    • Net Force: 5 N to the right

11. 

    • Thought Process: Forces are equal and opposite. They cancel each other out.
    • Net Force: 0 N

12. 

    • Thought Process: Forces are in opposite directions, so subtract them. 25N - 10N = 15N. The larger force is to the left, so the net force is to the left.
    • Net Force: 15 N to the left

13. 

    • Thought Process: Forces are in opposite directions, so subtract them. 40N - 30N = 10N. The larger force is downwards, so the net force is downwards.
    • Net Force: 10 N downwards