Lesson Plan
The Universal Pull: What Is Gravity?
Students will be able to explain that gravity is a universal force of attraction between objects that depends on their masses and the distance between them.
Understanding gravity helps students grasp fundamental concepts in physics, explain everyday phenomena like falling objects, and comprehend large-scale cosmic interactions, fostering a deeper appreciation for the universe.
Audience
7th Grade Students
Time
45 minutes
Approach
Through demonstrations, discussions, and a reading, students will explore and understand gravity.
Materials
- The Universal Pull of Gravity Slide Deck, - Dropping Objects Demonstration, - Gravity Misconceptions Reading, - Two objects of different masses (e.g., a textbook and a pen), and - Projector or interactive whiteboard
Prep
Teacher Preparation
15 minutes
- Review the The Universal Pull: What Is Gravity? Lesson Plan and all linked materials: The Universal Pull of Gravity Slide Deck, Dropping Objects Demonstration, and Gravity Misconceptions Reading.
- Gather two objects of different masses for the demonstration (e.g., a textbook and a pen).
- Ensure projector/interactive whiteboard is set up for the slide deck.
Step 1
What is Gravity?
10 minutes
- Begin with a Warm Up activity asking students to define gravity.
- Introduce the lesson using the The Universal Pull of Gravity Slide Deck (Slides 1-3) to define gravity as a universal force of attraction.
- Facilitate a brief class discussion on initial ideas about gravity.
Step 2
Dropping Objects Demonstration
10 minutes
- Conduct the Dropping Objects Demonstration using objects of different masses.
- Guide students to observe and discuss the results, challenging common misconceptions about how mass affects falling speed.
- Use The Universal Pull of Gravity Slide Deck (Slide 4) to explain the concept of air resistance.
Step 3
Mass and Distance Discussion
10 minutes
- Lead a discussion using The Universal Pull of Gravity Slide Deck (Slides 5-7) to explain how mass and distance influence gravitational force.
- Encourage students to provide real-world examples (e.g., Earth and Moon, sun and planets).
- Introduce the terms 'mass' and 'weight' and discuss their differences.
Step 4
Gravity Misconceptions Reading
10 minutes
- Have students independently read the Gravity Misconceptions Reading.
- After reading, facilitate a brief discussion to clarify any lingering misconceptions and reinforce correct understanding.
- Ask students to share one new thing they learned or had clarified from the reading.
Step 5
Cool Down
5 minutes
- Conclude the lesson with a Cool Down activity where students summarize the key factors affecting gravity.
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Slide Deck
The Universal Pull: What Is Gravity?
What makes things fall?
Why do we stay on Earth?
What keeps the planets in orbit?
Greet students and start with the warm-up activity. Introduce the topic of gravity, connecting it to their everyday experiences. Explain that gravity is more than just 'things falling down'.
Gravity: The Invisible Force
- Gravity is a force of attraction that exists between any two objects that have mass.
- It's a universal force, meaning it acts everywhere in the universe!
- It's what keeps your feet on the ground and planets orbiting stars.
Define gravity clearly. Emphasize 'force of attraction' and 'universal'. Ask students to think about examples beyond Earth.
It's Not Just Falling!
- Gravity is constantly at work, even when you don't notice it.
- It's pulling on everything, all the time!
- From an apple falling from a tree to entire galaxies interacting, gravity is the boss.
Introduce the idea that gravity isn't always obvious. Prompt students to think about how strong or weak gravity might be in different situations.
What Affects Gravity?
Gravity's strength depends on two main things:
- Mass: The more massive an object, the stronger its gravitational pull.
- Distance: The closer two objects are, the stronger the gravitational pull between them.
Explain how mass and distance are key factors. Use simple analogies. This slide can set up the dropping objects demonstration or follow it to explain observations.
Mass vs. Weight: A Key Difference
- Mass: The amount of 'stuff' an object is made of. It stays the same no matter where you are.
- Weight: The measure of the force of gravity on an object. It can change depending on the gravitational pull (e.g., on the Moon, you weigh less!).
Discuss the difference between mass and weight. Provide clear examples and ask students to differentiate in their own words.
Gravity in a Nutshell
- Gravity is a universal force of attraction.
- It depends on the mass of objects and the distance between them.
- Mass is constant, but weight changes with gravity.
Summarize the key takeaways and preview what's next (e.g., misconceptions reading or activity).
Activity
Dropping Objects Demonstration
Objective: To observe how different masses fall under gravity.
Materials:
- A heavy object (e.g., a textbook)
- A lighter object (e.g., a pen or a crumpled piece of paper)
Instructions:
- Hold the textbook and the pen at the same height in one hand.
- On the count of three, release both objects at the exact same time.
- Observe which object hits the ground first.
Discussion Questions:
- Which object hit the ground first? What did you observe?
- Did the heavier object fall faster than the lighter object? Why or why not?
- What force might be affecting the objects as they fall, besides gravity?
- Imagine repeating this experiment in a vacuum (a place with no air). What do you predict would happen? Explain your reasoning.
Reading
Gravity Misconceptions: Setting the Record Straight
Gravity is a fascinating force, but it's also one that often leads to common misunderstandings. Let's clear up a few of the biggest myths about gravity.
Myth 1: Gravity Only Affects Heavy Objects
Many people think that gravity only pulls on big, heavy things like planets or bowling balls. This isn't true! Gravity is a universal force, meaning it affects all objects that have mass. Every single atom in the universe exerts a gravitational pull on every other atom. It's just that the pull is so tiny between very small objects that we don't notice it in our everyday lives. The Earth has a huge mass, so its gravitational pull on us is very noticeable.
Myth 2: Heavier Objects Fall Faster
Did you drop a heavy book and a light piece of paper? You probably saw the book hit the ground first. This often leads people to believe that heavier objects fall faster due to gravity. However, this is a major misconception! In a vacuum (a place with no air), a feather and a bowling ball dropped from the same height would hit the ground at the exact same time. The reason the book fell faster than the paper in your experiment is because of air resistance. Air resistance is a force that pushes against falling objects. Lighter objects with a larger surface area (like a flat piece of paper) experience more noticeable air resistance, slowing them down more than a dense, heavy object.
Myth 3: There's No Gravity in Space
If you've seen videos of astronauts floating in space, you might think there's no gravity up there. This is also false! There is gravity in space. In fact, gravity is what keeps the Moon in orbit around the Earth, and the Earth in orbit around the Sun. Astronauts on the International Space Station (ISS) are actually experiencing about 90% of Earth's gravity. The reason they float is because they are constantly falling around the Earth, along with the space station, in what's called freefall. Imagine being in an elevator and the cable breaks – you'd feel weightless as you fall, even though gravity is still pulling on you. The ISS and everything in it are doing the same thing, just continuously around our planet.
Myth 4: Gravity Only Pulls Down
When we think of gravity, we usually think of things falling "down" towards the Earth. However, gravity is a force of attraction between any two objects with mass. This means objects pull on each other in all directions! You are pulling on the Earth with gravity, just as the Earth is pulling on you. The reason you don't notice your pull on the Earth is because your mass is tiny compared to the Earth's. So, while the Earth pulls you down with a strong force, your pull on the Earth is so small it's immeasurable in termsable effect. Gravity isn't just about "down"; it's about mutual attraction.
Warm Up
Gravity Warm Up: What Do You Know?
Instructions: Take a few minutes to answer the following questions to the best of your ability. There are no right or wrong answers here, just share your initial thoughts!
- What is gravity? Try to describe it in your own words.
- What are some things that gravity does? Give at least two examples.
- Do you think gravity is the same everywhere in the universe? Why or why not?
Cool Down
Gravity Cool Down: Reflect and Summarize
Instructions: Answer the following questions to reflect on what we learned about gravity today.
- In your own words, explain the two main factors that determine the strength of gravity between two objects.
- Briefly explain the difference between mass and weight.
- What was one new or surprising thing you learned about gravity today?