How Pushes and Pulls Change Motion
Students investigate how the strength and direction of a push or pull can change an object's speed or direction of motion.
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Pushes, Pulls, and Motion
A push moves an object away from the person or thing applying the force. A pull moves an object closer. Pushes and pulls can make an object start moving, stop moving, speed up, slow down, or change direction. The strength and direction of the push or pull matter. For example, gently pushing a toy car may make it roll slowly. Pushing it more strongly may make it roll faster and farther. If you push the side of a moving car, the car may turn. Pulling a wagon handle toward you makes the wagon move in your direction. The floor can also affect motion. A toy may roll more easily on a smooth floor than on a rough rug because the surfaces affect how the toy moves.
Predict What Will Happen
A prediction tells what you think will happen before a test. You can use what you already know about motion to make a prediction. Imagine placing a toy car at a starting line. What will happen if you give it a gentle push? What will happen if you push it strongly? You might predict, “The strong push will make the car travel farther than the gentle push.” You can also predict how direction changes motion. If you push the car toward the left, it should move toward the left. Share your prediction with your group. Take turns speaking, listen carefully, and ask questions about your classmates' ideas. The group should agree on test rules, such as using the same car, starting place, floor, and person for every trial.
Test Gentle and Strong Pushes
Place a toy car behind a starting line on a flat floor. First, give the car one gentle push. Watch how fast it moves and where it stops. Return the same car to the starting line. Next, give it one strong push in the same direction. Watch where it stops. Repeat each kind of push several times because the results may be a little different each time. Keep the test fair by using the same car, floor, starting line, and direction. Change only the strength of the push. One student can push, one can watch, and one can record. Follow the group's safety rules: keep the path clear, wait for your turn, and never aim the car at another person. Then switch jobs so everyone can participate.
Measure How Far It Moves
Measure the distance from the starting line to the front of the stopped toy car. Use a ruler, yardstick, or measuring tape with inches or centimeters. Begin at zero, not at the end of the tool. Keep the measuring tool straight along the car's path. Suppose the car moves 18 inches after a gentle push and 35 inches after a strong push. Record each number in a data table. Include the unit, because 18 inches and 18 centimeters are not the same distance. If the tool is too short, place a small marker at its end and continue measuring from that point. Ask a partner to check the tool's position and read the number with you. Careful measuring helps your group make a clear comparison.
Compare Results and Explain
Look at the distances in your data table. Compare the gentle-push trials with the strong-push trials. Which distances are greater? In one test, a gentle push may move the car 18 inches, while a strong push moves it 35 inches. This evidence supports the idea that a stronger push can make the same car move farther on the same surface. You may also notice that the stronger push makes the car start faster. Direction matters too: a push to the right makes the car move right, while a push from the side can make it turn. Take turns explaining what your group found. Listen attentively, respond to others' ideas, and use measurements as evidence. If results differ, discuss possible reasons, such as uneven pushes or a crooked measuring tape.