Click image to open full size
Push vs Pull
Forces That Change Motion
Related Labs
A push and a pull are both forces, which means they can change how an object moves or even change its shape. In everyday life, you push a door to open it away from you and pull a drawer to slide it toward you. Learning the difference helps students describe motion clearly and understand how forces act in real situations. This idea is a foundation for later topics such as Newton's laws, friction, and balanced versus unbalanced forces.
A push acts away from the source of the force, while a pull acts toward the source of the force. Either type of force can start motion, stop motion, speed an object up, slow it down, or change its direction if the forces are unbalanced. Forces are measured in newtons, and the total effect depends on both size and direction. When pushes and pulls cancel each other, the net force is zero and the object's motion does not change.
Key Facts
- A force is a push or a pull that can change motion or shape.
- Force is measured in newtons (N).
- Net force = sum of all forces acting on an object.
- If net force = 0, motion stays the same or the object remains at rest.
- F = ma, so a larger net force causes a larger acceleration.
- Pushes and pulls can be contact forces, while gravity is a noncontact pull.
Vocabulary
- force
- A force is a push or pull that can change an object's motion or shape.
- net force
- Net force is the overall force on an object after all individual forces are added with direction.
- acceleration
- Acceleration is the rate at which an object's velocity changes.
- friction
- Friction is a force that opposes motion between surfaces that touch.
- balanced forces
- Balanced forces are forces that cancel so the net force is zero.
Common Mistakes to Avoid
- Thinking a push always makes an object move and a pull always slows it down, which is wrong because either one can speed up, slow down, stop, or turn an object depending on direction.
- Ignoring direction when adding forces, which is wrong because forces in opposite directions subtract rather than add.
- Assuming an object moving at constant speed must have a force pushing it forward, which is wrong because constant velocity means the net force is zero.
- Confusing force with motion, which is wrong because an object can be moving even when no unbalanced force is acting on it.
Practice Questions
- 1 A student pushes a box to the right with 18 N while friction acts to the left with 7 N. What is the net force on the box, and in which direction does it act?
- 2 Two students pull a sled in opposite directions. One pulls left with 25 N and the other pulls right with 31 N. What is the net force and which way will the sled accelerate?
- 3 A book rests on a table while gravity pulls downward and the table pushes upward. Explain why the book does not accelerate.