ALEX Lesson Plan

In this lesson, which was adapted from Gravity and Falling Objects, students predict what will happen when different objects are dropped at the same time from the same height, and then test their predictions. Next, they will observe objects of different masses being dropped and leaking cups being dropped into a bucket. The activities in this lesson will demonstrate that all objects fall at the same rate, regardless of their mass. Finally, students will predict what will happen when two balls of the same mass but different volumes--and then two balls of different masses but the same volume--are dropped at the same time from the same height.

This lesson results from a collaboration between the Alabama State Department of Education and ASTA.

• chart paper
• hammer
• feather
• apples
• knife
• two balls of same mass, different volumes
• two balls of same volume, different masses
• foam cups (optional)
• various liquids, including water (optional)
• bucket (optional)

Galileo on the Moon

Galileo: His Experiments

What is Weightlessness?

We often take the force of gravity for granted, even though Earth's gravity is what keeps each of us from floating off into space! In this lesson, students begin to more fully understand and appreciate the force of gravity. They predict what will happen when a whole apple and half an apple are dropped at the same time from the same height then test their predictions. Next, they observe cannonballs of different masses being dropped out of a tower, and leaking cups being dropped into a bucket. These activities demonstrate that all objects fall at the same rate, regardless of their mass - a concept known as the law of falling bodies. Students then watch a video segment showing a NASA astronaut dropping a feather and a hammer on the Moon. They repeat the activity in the classroom then consider why these objects fall at the same rate on the Moon but not on Earth. Finally, they use what they have just learned to predict what will happen when two balls of the same mass but different volumes - and then two balls of different masses but the same volume -- are dropped at the same time from the same height.

Before Strategy/Engage

1. Find out students' ideas about gravity. Ask the following:

• What is gravity?
• Where is gravity?
• What does gravity do?

Give students time to explain their ideas. Record their thoughts on the board or on a piece of chart paper, so that you can return to them later.

2. Hold up a hammer and a feather and ask students to predict what would happen if you dropped them simultaneously from the same height: Would they hit the ground at the same time or at different times? Do not drop the objects at this point. Show students the Galileo on the Moon video. After screening it, ask the following:

• Did you expect the hammer and the feather to land on the surface of the Moon at the same time?
• Why do you think this happened?

During Strategy/Explore/Explain

3. Try investigating some of these questions about gravity. Ask students to predict what would happen if you dropped a whole apple and half an apple at the same time from the same height: Would they hit the ground at the same time, or would one hit before the other? Why? Have the students record their predictions and explain their thinking. Ask students to share some of their predictions. Then drop the apples. Allow time to discuss the results and for the students to try to explain the factors that produced them. Use this activity as an opportunity to discuss gravity as a force that pulls objects toward Earth.

4. Go to the Galileo: His Experiments interactive activity (Falling Objects experiment). Ask students to predict which cannonball will hit the ground first and give reasons for their prediction. Select their choice to see if their prediction was supported or not supported. Hopefully, at this point, students are willing to accept or at least consider the idea that all objects fall at the same rate, regardless of their mass. Galileo conducted several experiments and concluded that the effect of gravity on earthly objects is the same, regardless of the mass of those objects. He argued that in the absence of other forces such as air resistance, all falling objects accelerate toward Earth at the same rate.

5. Show the Galileo on the Moon video again. Remind students of the predictions they made in step 2 (would the hammer and the feather hit Earth at the same time). Try it. Then ask:

• Why did the hammer and the feather fall at the same rate on the Moon but not on Earth?

Introduce the idea of air resistance, a force (friction) that opposes any object moving through air. Ask:

• What role did air resistance play in the rate at which the objects fell?

6. Show the video What Is "Weightlessness"?. This demonstration can be interpreted as the water floating inside the cup, but from Galileo's experiments, we know that the water and cup are falling at the same rate even though their masses are different. Review what happened in the segment, and ask:

• Were you surprised that the water stopped pouring out of the holes in the cup once the cup started to fall?
• Can you think of an explanation for this based on your understanding of the way falling objects are affected by gravity?
• Why do you think the term weightlessness is used in the title of the video? (optional)

7.  Have students try the falling cup activity from step 6 in your classroom. Experiment with a variety of liquids. Ask students to first predict the results. Do they think they will get the same result no matter which liquid is used, or a different result? Ask them to explain their reasoning; see how well they apply what they have learned from previous investigations to these new situations.

Assessment: (Performance)

You are a team of engineers who have been given the challenge to design a parachute out of everyday items. Your challenge is to design a parachute that can carry one metal washer to the ground from a height of 2M and hit a 10 cm target with the slowest possible rate of descent. The parachute that can hit the target with the slowest descent rate is the winner. 

The assessment for this lesson will be a performance assessment.  Students will work in groups for this performance assessment. Please see the link entitled, "Playing with Parachutes": http://tryengineering.org/lesson-plans/playing-parachutes.

Extension/Acceleration

Using the paper material that worked the best, do the same activity testing the parachute size. Have students test circles with different radii to find the optimal size.

Try parachutes with and without holes in the top (and with different-sized holes).

Make parachutes using different materials, such as plastics, cotton and nylon.

Hold a competition to find a design that can land a toy vehicle most gently.

Remediation/Intervention

How Does a Parachute Works

Solar System 101

This website from NASA includes detailed information about the planets, including images of each planet and a 3D interactive, “Eyes on the Solar System.”

MSL Parachute Testing

Science of Swimming 

This TIME for Kids article shows how Olympic swimmer Missy Franklin uses her body and technique to fight against drag forces in the pool. The video is part of the “Science of the Summer Olympic Games: Engineering in Sports” video series from NBC Learn, the educational division of NBC News. (4:59)

Video: Science of Swimming Missy Franklin