## Pushing, Pulling, and Predicting Force Patterns

Physical science concepts related to forces are varied and the basics of pushes, pulls, and predicting how forces affect the motion of objects can be seen in many different ways. Helping students begin to discuss the disciplinary core ideas related to this topic can be accomplished through both common experiences and the use of children’s stories. Students must first understand how forces affect the interaction of objects before they can begin to consider types of forces and possible patterns. Younger students begin to consider how a snowplow can demonstrate both pushing and pulling as it saves the day. Older students revisit the idea of pushing and pulling before they start to think about recurring motions that are predictable in common everyday scenarios.

### Grades K–2: Pushing and Pulling

#### Purpose

Students will investigate that a push or a pull can have different strengths and how each can impact the motion of an object.

#### Materials

• The Little Snowplow
• box or bin full of books
• same type soccer or kickballs per pair of students
• Supplemental Resources (images, Pushes and Pulls Student Sheet): https://bit.ly/3gya5Tv
• Diagrams of pushes and pulls
• Videos that show objects being pushed or pulled (see Online Resources).

#### Engage

Begin the lesson by sharing the cover of The Little Snowplow with the class and asking them to describe what the little snowplow is doing in the picture. Allow students to share their ideas about moving snow or pushing the snow out of the way. Prompt the students to consider the following question as they listen to the story: Do you think that objects can be moved by pushes or pulls? As the story is read, stop, and discuss the following points with the students:

p. 2 – In the story, the big trucks point out that they can do the “heavy lifting”? What do you think is meant by heavy lifting?

p. 5 – Look at the photos closely; what do you think the little snowplow is doing to the balloons from the parade? What is it doing to the leaves? Is each a push or a pull?

p. 7 – Why do you think the little snowplow was waiting for snow? Have you ever seen a snowplow move snow? Can you describe how that is done?

p. 11 – In the story, the snowplow is doing exercises, and it says he pushed loads of gravel and pulled blocks of concrete. Do you think snowplows can really do exercises? Look closely at the pictures, describe what the snowplow is doing when it pushes, or pulls the objects.

p. 22 – Look at the photos; what do you think the little snowplow was doing in the top picture? In the bottom picture?

p. 24 – What is the little snowplow doing in the picture to help the dump truck? The story says “tugging,” do you think that is more like a push or a pull? Why?

p. 25 – When the little snowplow pulled the dump truck free, does the picture make it look like it was easy or hard? Why do you say that? When would pulling something be easy? When would it be hard?

Ask the students to return to the question, “Do you think that objects can be moved by pushes or pulls?” and discuss their answers and possible examples from the story.

#### Explore

Providing opportunities for young students to investigate pushes and pulls will help them understand how different forces affect objects and understand how objects can be placed into motion. Ask the students to think about where the Little Snowplow was located when it moved the snow in the story. In what direction did both the snowplow and the snow move? Repeat this question when the Little Snowplow was trying to pull the dump truck free. Using the diagrams provided in the Supplemental Resources, project these diagrams onto the board and allow the students to draw arrows helping to illustrate the directions each moved. Ask students to make observations about what direction each moved. What position are both in when the Little Snowplow exerts the force, and where is the object moved to in each diagram? Now that students have had an opportunity to consider differences about pushes and pulls from where the different objects are that are involved in the process of push and pull, tell them that they are going to participate in some different investigations and determine if it is a push or pull and if they are starting or stopping the object from moving.

Investigation 1: Moving Objects

Teacher note: It is best to do these investigations on a smooth floor such as a hall with linoleum. While friction still exists, it will be less than if on the carpet. In this investigation, students are asked to move different objects using both pushes or pulls. Provide the students a box or plastic file tote that is filled with books or something heavy. Place the box on an X on the floor and place a “finish line” about 10 feet from the starting point. Using pairs of students, ask the students to determine what is the best way to move the box to the finish line. Remind students of safety and ask them to be cautious as they participate in moving the box and have adult spotters available if possible. When pairs are done investigating which might be the best way to have the box cross the finish line, ask them to describe their answers using arrows on the Pushes and Pulls student data sheet (see Supplemental Resources).

Investigation 2: Stopping Objects

Take the students into a gym and provide each pair with a soccer ball or kickball. Demonstrate for the students what happens when the ball is pushed toward a wall. Prompt them to consider the following questions: When I reached out to start the ball moving, do you think it involved a push or a pull? If so, which one? What type of force was used to start the ball rolling? What stopped the ball? Then ask the students to kneel on the floor and push the ball to their partner (Safety note: Do not let the students kick the ball at each other). Have the partner stop the ball with their hands when it comes to them. Ask the students to consider the following questions, “What stopped the ball? When you reached out to stop the ball, do you think you used either a push or a pull? Can you describe how?” Ask the students to return to their student sheet and illustrate where pushes and pulls might occur with the moving soccer ball.

Investigation 3: Different Strengths

Review with the students what they were able to observe in the first two investigations. In investigation 1, students explored the difference between a push and a pull and discussed what might be easier in moving the box. In investigation 2, students observed that objects could be started with a push and stopped or have their direction changed with a push. Explain to the students that they will repeat part of investigation 2 where they pushed a ball. However, this time, they will push the ball toward the wall, and their partner will observe what happens to the balls when different people push them and then what happens when they hit the wall. Ask half of the class to all sit at the start line in the same way such as criss-cross legs, to place the ball directly in front of them with their hands behind the ball. They should lean forward and on the count of three, push the ball toward the wall. Their partners should observe what is happening to the different balls in terms of speed at first and then what happens when the balls hit the wall and roll backward. Questions to help students think about what they observed include: Were all balls in a line when the students had them in front of them before starting? What happened when the students pushed the balls forward? Did they stay in that same line? What do you think caused a difference in the speed of the ball moving forward? What happened when all the balls hit the wall? Ask students to return to their student sheets and sketch what they observed and use arrows to indicate which direction the push or pull was and what direction the ball traveled at first. Ask students to also indicate what happened when the ball hit the wall.

#### Explain

Bring the class back together and ask them to share their findings from the investigations by responding to the following questions:

• Can you describe a push or a pull in your own words? What causes an object to move when it is pushed or pulled?
• In Investigation 1, describe what happened when you pushed the box? Pulled the box? Where were you in comparison to the box for each movement?
• In Investigation 2, what did you notice about the ball when you pushed it? And when the wall stopped it?
• Are all pushes and pulls the same strength? What happens when a stronger push is used?
• Now ask the students to return to the following points from the story and connect the story to their understanding of a push or a pull.
• Where in the story did the Little Snowplow push objects? Pull objects? Can you give an example of where you were pushing objects in your investigations? Pulling objects?
• Why do you think the Little Snowplow needed to pull the dump truck out from where it was stuck rather than push it out?

#### Elaborate

In this section, students are shown a variety of different video clips where they are asked to determine if the action being demonstrated represents a push or a pull (see Online Resources).

Pull Videos:

• Tug of War (pull is in both directions). Questions to engage students include, what could happen if one side had three people?
• Grocery wagon. Before showing the video, ask which direction will both the cart and the man travel.
• Pulling a wagon. Do you think it would be easier or harder if there were two people in the wagon?
• Wheeled Suitcase. What would happen to the suitcase if the person was walking faster?

Push Videos:

• Grocery Cart. What would change if there were more groceries in the cart?
• Pushing a Stroller. Would the woman need to push the stroller as hard if she wasn’t going uphill?
• Wheelbarrow. How does the wheel help make the wheelbarrow easier to push?

#### Evaluate

Throughout the lessons and investigations, the student demonstrates their initial understanding by describing how the Little Snowplow pushes or pulls different objects. As students complete the investigations, they are describing what a push or pull is in their own words and demonstrating how a push or pull can stop or start an object’s motion or change the direction of an object’s motion. Finally, students are applying their understanding of these core ideas by describing if a push or a pull is occurring in everyday actions.

#### Purpose

Students will describe how different objects move and predict future motion based on observations of force and motion.

#### Materials

• Just a Little Bit
• online simulations (see Online Resources)
• chart paper, dental floss or fishing line, lead fishing sinkers, meter sticks.
• Supplemental Resources (pictures, Force and Motion student sheet): https://bit.ly/3pZq4gp
• pendulum setup

#### Engage

Show students the series of pictures that illustrate a common everyday object being acted on by a force (see Supplemental Resources). Ask them to explain what is happening in the photos and what they think will happen next. Help the students consider what is happening in each photo by prompting them with questions about the action.

Child on swing – Describe what you see happening. The swing with the girl in pink is up in the air; what will happen to the swing next? The other swing has a child that is just about to start swinging. Think about when a child starts to swing—where do they start? How does a swing or pendulum keep moving? How can an adult or friend help get the swing moving? What kind of force could they apply?

Seesaw – If you look at the first picture of the seesaw, what do you notice about each side? Do you think the seesaw will move? What happens if the young girl pushes up with her legs? What would happen to the seesaw then? Now look at the second picture, do you think the seesaw will move now? What do the children on each side need to do to keep the seesaw moving? What kind of force are they using?

Ball and Half Pipe – What do you think would happen if the ball is placed at the bottom of the half pipe? What about if it was placed at the top of one side? What kind of force would be acting on the ball then?

#### Explore

An object’s motion may be predicted by observing and measuring past motion of the object. Students need to be able to connect their understanding of forces that they previously learned to how those forces act on objects now. Provide students opportunities to conduct each of the following investigations. Ask students to form groups of four that will allow them to discuss their ideas in small groups. As students explore each station, ask them to sketch and include their observations on the Forces and Motions Student Sheet (see Supplemental Resources).

Station #1: The Motion of a Pendulum

The motion of a swing is similar to a pendulum. Demonstrate for students how to set up a pendulum using dental floss or fishing line and a finishing sinker from the edge of a table (see Supplemental Resources). Model for the students how to measure the height from the floor from which to start the pendulum swinging by pulling the sinker back to that point and releasing it. Using a meterstick on the other side, ask the students to measure how high the pendulum swings and what happens after subsequent swings. The pendulum eventually comes to a stop as gravity acts on it. Ask the students to repeat this process using different heights from which to drop it each time.

Station #2: Seesaws

In this particular station, students need to consider what happens when a seesaw is used. Locate a playground with seesaws or if not possible, a video can be used as a replacement. In this station, ask the students to determine how the seesaw moves when each side is balanced with approximately the same mass (kids). Does it move up or down when they just sit there? What needs to happen for one side to go up while the other side goes down? What needs to happen to continue that motion?

Station #3: Half Pipe

If there is the possibility of locating a half pipe model that is made with building tools such as pipe insulation or even toys, that would be the first recommendation. However, if unable to do so, the teacher can utilize the simulation found at pHet to allow students to make observations and then discuss what happened (see Online Resources). Using the Intro simulation (which does not add the influence of friction), place the skateboarder at the top of one side and ask the students to predict what will happen. Once students have had a chance to make those predictions, start the simulation at normal speed and ask the students to continue to make observations. Discuss if their predictions were accurate? Then repeat the simulation using the option where friction is part of the simulation. How did the two different runs differ? Which one would be more accurate in a real situation?

#### Explain

When students finish their exploration of the stations, return the photos from the engage stage to the board and ask the student to revisit the questions for each picture. While students are considering the answers to the questions below, ask them to also include terms such as force and motion to help describe what was happening. Add the following questions to each picture.

Child on swing – How is this picture similar to the pendulum you created? What would happen if someone could pull you all the way back on the swing and let you go?

Seesaw – If students on the seesaw did absolutely nothing to help move it, would it move? Why or why not?

Ball and Half Pipe – In the two different simulations you saw, one showed what happened when NO friction was involved and the other when there was friction involved. Since friction slowed down the skateboarder, do you think it is a force? Why or why not?

#### Elaborate

In the activity with a seesaw, students looked at forces and predicted the motion that would happen if the sides were balanced. Discuss student understanding of balanced and unbalanced forces. Share the story Just a Little Bit with the students and ask them to connect their understanding of forces to the story. Stop and discuss the following points.

Inside title page – In this story, two friends, a mouse and an elephant, want to use the playground equipment. What would happen to the mouse if elephant let go of its hand right now? Why do you say that? Can you give an example in real life similar to this situation?

pp. 2–3 (Cover the last sentence so students need to answer the following question) Look at elephant and mouse on the seesaw. What do you think will happen when mouse gets to the end? Can you explain your answer?

pp. 4–5 Why do you think elephant was saying “push down” to the mouse? Describe the forces that you see happening on these pages. What would happen if elephant pushed up with his legs?

pp. 8–9 Describe what is happening related to forces as more animals sit on mouse’s side.

pp. 20–21 After many more animals join mouse, elephant is still saying “push down.” What needs to happen for mouse’s side to actually move toward the ground?

pp. 26–29 Describe what happened finally when elephant’s side of the see saw went up in the air. Describe where forces are applied to the see saw. Are they the same? Different? Elephant has his legs up on the seesaw. What will need to happen for all of the animals to keep going up and down?

#### Evaluate

At the start of the lesson, students demonstrate a basic understanding of how different objects move and be able to predict their pattern from experience. As they engage in the stations, they begin to connect their initial understanding to the core ideas about force and motion. Finally, they are asked to describe the situation presented in the story and predict what will happen as more animals join on the seesaw.

#### Online Resources

pHet Half Pipe Intro Simulation

pHet Half Pipe Simulation with Friction

The following videos come from Pexels. You may be prompted to create a free account, but the URLs link to videos that are free to use.

Grocery Car

Grocery Wagon

Tug of War

Red Wagon

Traveler with Wheeled Suitcase

Stroller

Wheelbarrow

Christine Anne Royce (caroyce@aol.com) is a professor at Shippensburg University in Shippensburg, Pennsylvania, and past president of NSTA.

Literacy Physical Science Early Childhood Elementary