IV.3.E.2

Benchmark 2
Explain how forces (pushes or pulls) are needed to speed up, slow down, stop, or change the direction of a moving object.

Benchmark Clarification

An object moves in a straight line and at a constant speed as long as balanced forces act on it. When a force acts on an object, it can speed up the object’s motion, slow it down, or change its direction. The greater the force acting on the object, the greater the change in the object’s speed and/or direction. Friction is one force that makes an object decrease speed, when no other pushes or pulls (forces) appear to be acting upon it.

Students will:

* Demonstrate and describe the motion of objects
* Investigate the forces that make an object move

Descriptions should include:

* Friction — a force that works against motion
* Gravity — a force that makes things fall toward the center of the Earth
* Other pushes or pulls — forces exerted by people and machines

Key Concept / MEAP Vocabulary
Changes in motion:

* speeding up
* slowing down
* turning

Common forces:

* push
* pull
* friction
* gravity

Size of change is related to strength of push or pull

Real World Context

* playing ball
* moving chairs
* sliding objects