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Lesson Plans

Push, Pull and Weight

Summary

Grade Range
Kindergarten
Group Size
2 students
Active Time
50 minutes
Total Time
50 minutes
Area of Science
Physics
Key Concepts
Push, Pull, Motion, Weight
Credits
Sabine De Brabandere, PhD, Science Buddies Alumni
Science Buddies is committed to creating content authored by scientists and educators. Learn more about our process and how we use AI.
Drawing of two soccer balls rollingImage Credit: Sabine De Brabandere, Science Buddies / Science Buddies

Overview

Experimenting with balls is fun! In this hands-on lesson, you and your students will make them collide and study how balls can push each-other and people too! While exploring, students will also feel how pushing a light ball is different from pushing a heavier ball. Weight is important.

This lesson fits well together with a lesson where students push balls to discover how people use pushes and pulls to change motion.

Learning Objectives

NGSS Alignment

This lesson helps students prepare for these Next Generation Science Standards Performance Expectations:
This lesson focuses on these aspects of NGSS Three Dimensional Learning:

Science & Engineering Practices
Planning and Carrying Out Investigations. With guidance, plan and conduct an investigation in collaboration with peers.
Disciplinary Core Ideas
PS2.A: Forces and Motion. Pushes and pulls can have different strengths and directions.
Pushing or pulling on an object can change the speed or direction of its motion and can start or stop it.

PS2.B: Types of Interactions. When objects touch or collide, they push on one another and can change motion.

PS3.C: Relationship Between Energy and Forces. A bigger push or pull makes things speed up or slow down more quickly.
Crosscutting Concepts
Cause and Effect. Simple tests can be designed to gather evidence to support or refute student ideas about causes.

Materials

Two baseballs next to a wiffle ballImage Credit: Sabine De Brabandere, Science Buddies / Science Buddies

For each group:

For the entire class:

Background Information for Teachers

This section contains a quick review for teachers of the science and concepts covered in this lesson.

Students know from experience how pushing or pulling on an object can affect the object's motion. Maybe they explored how their own actions influence the motion of objects in a science lesson similar to this Push and Pull lesson plan. In this lesson, they will generalize this concept by seeing how objects can push or pull on other objects, as shown in Figure 1.

Drawing of a car smashing into the back-end of another carImage Credit: Sabine De Brabandere, Science Buddies / Science Buddies
Figure 1. A car crashing into an other car is an example of an object pushing another.

People can change the motion of objects by exerting a push or pull on the object. For example, you push a box to make it move, and you push harder to make it move faster. In a similar way, objects can push or pull another object. If a minivan runs into the rear of a small sports car waiting at a red light, both cars will push each other and consequently change their motion. The sports car will speed up, and the minivan will slow down. If it runs into a heavy truck, the heavy truck will hardly change its motion. That shows how the result of a push depends on the weight of the object being pushed. In this lesson, students will explore all this by rolling balls into each other. During the collision, the balls push each other just like the colliding cars push each other, and the pushes will change the motions of both balls.

The size of the push plays a role in its impact as well. This influence is studied in the introductory lesson on Push and Pull.

Technical note:

The term weight is used throughout this lesson to refer to how heavy an object is. In everyday language, weight and mass are often used interchangeably, but in science they have different meanings. Mass is a measure of how much "stuff," or matter, makes up an object. An object's mass does not depend on gravity, so it does not change based on your location (an object has the same mass on Earth and on the Moon). Weight is a measure of how hard gravity pulls on that mass, which changes with location (an object weighs more on Earth than it does on the moon). Technically, the impact a force (a push or a pull) has on an object's motion depends on its mass, not its weight. However, in the Next Generation Science Standards, students are not expected to differentiate between mass and weight until middle school, so it is OK to use "weight" with kindergarteners.

Additional Background Links

The following resources provide more information on how pushes and pulls (or forces) impact motion:

The following reference can help clarify the difference between mass and weight:

Teacher Tool Box

Related Lessons

Engage (10 minutes)

  1. Make a demonstration. Give a toy car a push so it gently collides with another toy car. Ask the students what just happened. Guide them to make detailed observations of how both cars move just before and just after the collision. Then, ask them to predict what would happen if the small toy car collided with the heavier toy truck. Jot down student's answers so you can come back to this, but do not correct.
  2. Optional: Read the book Everyone Shouted Pull written by Claire Llewellyn and illustrated by Simone Abel.
    Ask:
    Ask the students how the goods were transported to the market.
    Discussion tip:
    The goods were placed in a cart, and donkeys pulled the cart to get it moving.
    Ask:
    Was it easier to pull the cart when they returned from the market? Why was this the case?
    Discussion tip:
    No, the job was not easier because the cart was now full of animals. Pulling an empty cart would have been easier.
  3. If you did not do the first lesson plan, this lesson assumes students understand the words "push" and "pull" and have some understanding of the effects pushes and pulls have on the movement of objects. Refresh students' knowledge with this game.
    1. Let the students sit in a circle. Use a ball and let students push the ball to a friend while stating "I push the ball to Katy. " (replace the name Katy with the friend's name). Emphasize that during the game, the ball needs to stay on the ground. It cannot be thrown or picked up. The friend on the receiving end can stop the ball and push it to another friend or push it while it is still rolling to redirect it to another student. She also states, "I push the ball to ....". Play this until all the students have pushed the ball at least once.
    2. In a second phase, ask the student to push the ball harder. Point out how the ball rolls faster.
    3. In a last phase, ask the students to push the ball gently. Point out how the ball moves slower, and how the receiver might need to pull the ball towards him/her to get it.

    End by helping student conclude that a push or pull makes a ball move, and that a hard push or pull makes the ball roll fast, and a gentle push or pull makes it move slower. Students should understand this before they continue with the lesson.

  4. Introduce the experiment.
    Ask:
    What do you think will happen if I place another ball in the middle of our circle?

    If you did the first lesson plan but not the game, you can refer to the experiments where students roll one ball to each other.

    Discussion tip:
    Listen to students answers. If necessary, ask if they think the ball might roll into the ball that is in the middle.
    Ask:
    If the balls collide, or hit each other, what do you think they will do?
    Discussion tip:
    The students might state: "the balls will stop!", "the balls will fly up in the air!", or "the balls will pop." Listen to the students' predictions, but do not correct. Write them down with a few words or drawings so students can come back to it later in the lesson.
    Ask:
    How can we find out if our predictions are correct?
    Discussion tip:
    Listen to the students' ideas. Students might suggest testing it out. Testing is a great idea. Explain that you want all the students to perform tests because if everyone gets the same results, you will know the results are accurate and true.

Explore (30 minutes)

  1. Create an open floor space where students can roll the balls in pairs.
  2. Divide the class into pairs. Provide each pair with two identical balls (the heavier balls) and have them sit on the ground a few feet apart.
  3. State the rules: the balls need to stay on the ground at all times.
  4. Explain the goal: they will make one ball hit another ball and see what happens.
  5. Let students explore rolling the ball(s) to each other.
  6. For each experiment listed below:
    1. Ask a student to state what they want to find out.
    2. Ask students to discuss what they think will happen with their partner.
    3. Let students explore. Give guidance where needed.
    4. Let students explain their findings to each other.
    5. Bring their attention back to you and let the students report their findings.
    6. Demonstrate the reported ideas for the class, or let a student demonstrate the ideas.
    7. If you have a board available, make a quick drawing of the findings on the board. If you have the possibility to display a slideshow in the open area, this slideshow contains a graphic connected with each experiment.
    8. Show or let students show an example of this situation with toy-cars.

The class can move through the experiments together, or groups can be guided individually so they can discover at their own pace. All students should be asked to make clear observations of what happens, and make an effort to explain why it happens. Ask questions about speed and direction to more advanced students. For struggling students, use the experiments to reinforce that pushing an object makes it move or changes its movement. Walk around, ask questions and observe students to monitor if they follow along and understand the concept. If needed, guide them with follow-up questions and hints.


Experiment 1: What happens if one ball rolls into an identical ball that is stationary?

Guidance: Ask one student to place a ball in the middle. Ask the students what they can do with the other ball so it collides with the stationary ball.

Discussion tip:
The ball that is hit rolls away. The ball that is rolling hits, or pushes, the ball that is sitting still. This hit, or push, makes it move. Let more advanced students discover that the ball moves in the direction in which it is pushed. You might need to explain that the direction indicates where the ball is heading to.

The movement of the rolling ball changes too. It slows down or stops rolling. It was also pushed when colliding with the stationary ball.

If students use different words to indicate a push or pull, repeat their answers using the words "push" and "pull". For example, if a student states that "the ball is hit by the rolling ball" you could state, "Hitting is a form of pushing, so the ball is pushed by the rolling ball."

Demonstrate how pushing the stationary ball directly with a hand, or by rolling another ball into it, can both have the same result (the second ball rolls away). Let students repeat the demonstration.

If you have a board available, you can draw Figure 2 to represent the findings. This figure is also included in the slideshow.

Let a toy-car roll into a similar toy-car. Ask students if the same conclusions are valid.

Drawing of a soccer ball impacting a stationary soccer ball and transferring its forceImage Credit: Sabine De Brabandere, Science Buddies / Science Buddies
Figure 2. Illustration of what happens when a ball rolls into an identical ball. The blue arrow indicates the speed of the ball. A longer arrow means a faster moving ball.

Ask:
Are our findings the same as what we predicted?
Discussion tip:
Look back at the predictions the students made. Maybe some were correct, and probably, there were other predictions as well.
Ask:
Could there be some cases where if two balls collide, they do something else? (show a smaller lighter ball as you ask this question.)
Discussion tip:
Guide the students so they come up with the situations that are describe in the experiments below. These experiments can be done in any order. It is also not necessary to do all the experiments. Experiment four and five are ideal to keep fast-moving groups engaged.


Experiment 2: What happens if a lighter ball collides with a much heavier ball that is stationary?

Provide the students with the lighter ball if you did not already do so. Ask how these balls are different from the balls they already have. Students will feel how one is lighter than the other, it does not contain as much material.

Guidance: Ask one student to place the heavier ball in the middle. Ask the students what they can do to make the lighter ball roll into the heavy ball.

Let the students play for a few minutes, then ask the students how this experiment differs from the first experiment, where a heavy ball rolls into an equally heavy ball.

Discussion tip:
Depending on the situation, the heavy ball might stay still or move slightly. The movement of the lighter ball colliding with the heavy ball changes, mainly in direction. The light ball pushes the heavy ball but because it is so light, it can only push lightly. Advanced students might understand that the light ball is being pushed by the heavy ball too. A possible scenario is illustrated in Figure 3.

Demonstrate how the light ball can only create a small movement of the heavier ball. Compare this to you giving the heavy ball a light push. Let students repeat the demonstration. In both cases, the heavy ball hardly moves. You can conclude that the light ball could only create a small push.

If possible, draw Figure 3 to represent the findings or show the associated figure in the slideshow.

Ask a student how they could act out this situation with cars. Guide students in doing this experiment.

Drawing of a lighter ball impacting a heavier stationary ballImage Credit: Sabine De Brabandere, Science Buddies / Science Buddies

A ball rolls towards a stationary ball that has more mass than the ball that is rolling. Upon impact the ball with more mass will move slightly while the ball with less mass will deflect and continue to roll but in a different direction.


Figure 3. Illustration of what happens when light ball rolls into a much heavier ball.

Experiment 3: What happens if a heavier ball rolls into a much lighter ball that is stationary?

Guidance: Ask one student to place the lighter ball in the middle. Ask the students what they can do to make the heavier ball roll into the lighter ball.

Let the students play for a few minutes, then ask the students how this experiment differs from the first experiment, where a heavy ball rolls into an equally heavy ball.

Discussion tip:
The lighter ball that is hit rolls away. This time, it rolls away at higher speed, it rolls faster. It is pushed by the rolling heavy ball, so it starts moving in the direction it was pushed.

Challenge your students to find out why this lighter ball rolls away so fast, faster than when the same heavy ball pushed another heavy ball (seen in the first experiment). They might answer that the ball running into it caused a big push, and a big push can create more movement. This is correct. But in both experiments, the same heavy ball creates the push. The pushes are similar but the balls being pushed are different. One is heavier than the other. This leads us to believe that a lighter ball will move more when pushed compared to a heavier ball. Demonstrate by pushing with about the same force on the heavy ball and on the lighter ball. The students should see how the lighter ball rolls off with more speed and rolls further. Let the students try this out themselves.

This explains why the lighter ball moves away fast while the movement of the heavier ball rolling into it only changes a little. A visual representation of what happens is shown in Figure 4.

You might need to clarify that speed is a measure of how fast something moves.

Ask the students how this situation can be acted out with toy cars.

Drawing of a heavier ball impacting a lighter stationary ballImage Credit: Sabine De Brabandere, Science Buddies / Science Buddies

A ball rolls towards a stationary ball that has less mass than the ball that is rolling. Upon impact the ball with less mass will absorb some force from the larger ball and move quickly in the same direction of the impact. The ball with greater mass will continue rolling in the same direction as the impact but with less speed.


Figure 4. Illustration of what happens when a heavier ball rolls into a much lighter ball.

Experiment 4: What happens if two identical balls are both moving towards each other and roll into each other?

Guidance: Use the identical (heavier) balls. Both students sit a few feet from each other and roll the balls towards each other, so they collide.

Discussion tip:
The colliding balls change motion, and therefore, they must push each other. The outcome will depend on the speed at which the balls are moving before the collision. In general, both balls will change direction and speed in a similar way. Figure 5 provides an example where both balls roll into each other with similar speeds and change direction to roll away from each other with similar speeds.
Drawing of identical balls impacting each otherImage Credit: Sabine De Brabandere, Science Buddies / Science Buddies

Two identical balls that roll towards each other will transfer their energy to each other equally. Upon impact both balls will bounce off of each other and continue rolling at a similar speed but in opposite directions then they were originally traveling in.


Figure 5. Illustration of what happens when identical balls roll into each other.

Experiment 5: What happens when a lighter ball rolls into a moving heavier ball?

Guidance: Use the balls of different weight. Both students sit a few feet from each other and roll the balls towards each other, so they collide.

Discussion tip:
The balls push on each other when colliding, and as a result, their movement will change. How much their movement changes will depend on the speed at which the balls are moving before the collision. In general, the lighter ball will drastically change its movement while the heavier ball will only slightly change its movement.
Drawing of a heavier ball impacting a lighter ballImage Credit: Sabine De Brabandere, Science Buddies / Science Buddies

Two balls of different masses roll towards each other at the same speed. Upon impact the ball with less mass will bounce off of the ball with larger mass and will travel faster than its original speed but in the opposite direction. The ball with more mass will absorb the impact and continue traveling in the same direction but will less speed.


Figure 6. Illustration of what happens when a heavy ball and a lighter ball roll into each other.

Reflect (10 minutes)

Ask:
What did we learn about what happens when two balls collide?
Discussion tip:
When balls collide, they push each other. As a result, the balls will change movement. They might start moving, slow down, change direction or a combination of these.

For more advanced students, add that we also learned that when a lighter and a heavier ball are pushed in the same way, the lighter ball will change its movement more compared to the heavier ball. We could also see that if a heavier ball and a lighter ball roll at a same speed, the heavier ball will create a bigger push when colliding with another ball.

Ask:
Do you remember the demonstration with the toy cars? We predicted what would happen if the small toy car collided with the heavier toy truck. [quickly summarize their predictions] Do you think our predictions were correct? Can you use what we learned in this lesson to convince me that your answer is correct?
Discussion tip:
The answers will depend on what the students predicted. The case where a lighter ball collides with a heavier ball can be used to predict what will happen when a small toy car collides with a heavier toy truck.
Ask:
You just saw how balls can push each other when they collide. Can other objects push or pull each other too? Can you give some examples?
Discussion tip:
Yes, other objects can push and pull each other too. Your students might give examples like a bulldozer pushing dirt, a crane pulling up boxes, a tow truck pulling a car, or the locomotive pulling a caboose. Other examples are a broom pushing dust away, a hammer pushing on a nail, two toy cars colliding, a pencil rolling into another pencil, a person pushing a cart, or a ball rolling into a person and pushing him/her, etc. Make sure to add some examples students can relate to.

Explain to students how the wind can push too. It can make a leaf, a boat, or your hair move. Other examples are waves pushing sea shells up on the beach, or the wind pushing on them or their kite.

Ask:
We also saw how heavy balls need a bigger push to change their movement compared to lighter balls. That is true for other objects too. Can you give some examples where a heavy object needs a bigger push compared to a lighter object?
Discussion tip:
Your students might give examples like a heavy box compared to an empty box, a heavy cart compared to an empty cart, a loaded train compared to an empty train, a real car vs a toy car, an elephant vs a mouse, etc.

Indicate that size is not always a good indication of weight. A beach ball is lighter than a baseball, but it is also bigger.

Optional: You can provide your students with the worksheet. This will solidify the concepts.

Assess

Walk around in the class while the students perform their experiments. Ask questions to see if students follow along and grow a deeper understanding.

Identify some things that can move when a ball rolls into it. Ask your student to state what will happen to that object when a balls rolls into it, and why this would happen. Examples are a cup, a small toy-car, another ball.

Identify some things that move around the school or examples students know well. Ask your student to state what makes it move, is it a person pushing or pulling, or is it something different that pushes or pulls? Some examples are

  • A person can kick (push) or throw (push) a ball.
  • The ball can knock over (push) a stack of cans.
  • For advanced students: A broom can sweep (push) fallen leaves.
  • For advanced students: A person can throw (push) trash into the trashcan.
  • For advanced students: A student can pull another student over the line.
  • For advanced students: A train engine can pull the wagons.
  • For advanced students: A tow truck can pull a car.
  • For advanced students: A person can push or pull a door to open it.
  • For advanced students: The wind might make the flag move (push).

Place a clearly filled box and a similar empty box next to each other. Ask the student which one will be easier to move when a ball rolls into them. Ask the student to explain their prediction. Let the student test it out and explain why their prediction is correct or different. For advanced students, ask which one would be easier to move by pushing the boxes.

If students can list examples of objects rolling into each other and can correctly predict the objects will change their movement because of the collision, they have sufficiently mastered this concept. Students should also start to understand that heavier objects are harder to move compared to lighter objects.

Make Career Connections

Discussing or reading about these careers can help students make important connections between the in-class lesson and STEM job opportunities in the real world.

Physicist
Add Favorite
Career Profile
Physicists study the world around them. They look at how things move, push, and pull each other. They not only look at ordinary objects like balls, cars and books, but also at tiny objects, so small you cannot see them with your eyes, or huge ones like planets. Read more
Automotive Engineer
Add Favorite
Career Profile
Engineers are people who build and design things. There are many different types of engineers. Aerospace, automotive, and robotics are a few examples. Engineers might need to find out how strong a train engine needs to be, so it can pull a heavy train over a mountain. Read more

Lesson Plan Variations

  • A bowling game where students roll balls and try to hit a stack of cans can be a nice extension of this lesson. Have a stack of heavy and a stack of light cans. Use heavy and light balls. Can the students predict which combination would knock down the most cans? Let students explain their reasoning to support their prediction.
  • Machines often have moving parts that push each other. Show students the parts of simple machines to demonstrate the push action. Open a manual pencil sharpener and turn the crank by pushing it, thus pushing some gears and making them rotate. The last gear is attached to the blades, which slide against the pencil and sharpen it. A doorknob is another example. Turn a doorknob to make the latch move in and out. A more complex example where you can see the connecting parts is a bike. Show students the different parts of a bike while you explain how the parts push and pull on each other. You push the pedal, this makes the gear rotate, which sets the drive chain in motion. This makes the rear gear rotate. The rear gear is attached to the back wheel(s), so they start moving too.

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