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Forces and Newton’s Laws of Motion- Study Guide
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Newton’s Laws of Motion are universal- they explain all observable motion in the universe.
A Force is a push or a pull.
Forces can be BALANCED: these cancel each other out and cause no change in motion.
Forces can be UNBALANCED: these do not cancel each other out and cause some change in
motion. (the net force is not zero)
5. The sum of all forces is called the NET FORCE.
6. Newton’s 1st Law of Motion= an object at rest or moving at a constant speed in a straight line
will continue to do so until a net force (unbalanced) acts on it.
7. FRICTION is the force that acts against motion by two surfaces touching.
8. Newton’s 2nd Law of Motion= an object acted upon by a net force will accelerate (F=ma) in the
direction of the net force.
9. For example, a force of 10 Newtons would cause a 5kg object to accelerate at 2 m/s/s.
10. Question: how much force is required to cause a 10 kg object to accelerate at 5 m/s/s? Answer:
50 Newtons.
11. WEIGHT is a measure of the force of gravity on an object. Weight and Mass are not the same
thing. Weight can change if gravity changes.
12. Newton’s 3rd Law of Motion= For every action force there is an equal but opposite reaction
force.
13. Example of 3rd Law: a baseball strikes a bat. The ball applies a force to the bat (ACTION). The bat
applies a force to the ball (REACTION).
14. Example of 2nd Law: the ball accelerates more than the bat because it has smaller mass.
15. CENTRIPETAL FORCE: the force that hold an object in a circular path.
16. CENTER OF MASS: the around which an object will rotate if thrown.
17. FREE FALL: a state of weightlessness caused by continually falling around the Earth (example:
space station)
18. Falling objects are accelerated by GRAVITY. They fall faster until they reach TERMINAL VELOCITY.
19. Terminal velocity is the speed at which air resistance causes a falling object to stop accelerating.
20. Any object that is launched into the air with horizontal velocity will follow a curved path due to
2 or more forces (including gravity) acting on it at once. These objects are called PROJECTILES
and they exhibit PROJECTILE MOTION.