1st Law of Motion:
An object at rest will remain at rest, and an object moving at a constant velocity
will remain at that constant velocity, unless it is acted upon by an unbalanced
force.
** An object will stay the way it is (in motion or at rest ) until a unbalanced force acts on it. **
Example: your notebook resting on your desk will not slide off without a force (gravity / push or pull )
Gravity and friction are unbalanced forces that often change an objects motion.
Inertia- resistance to a change in motion
Depends on mass:
Greater mass = more force it will take to put the object in motion = greater inertia.
2nd Law of Motion:
Acceleration depends on the objects mass and on the net force.
Force = mass x acceleration
Example: It is easier to roll a chair with one text book than it is to roll a chair with 10 text books in it.
How much force is needed to accelerate a 1400 kilogram car 2 m/s2?
F= M x A
F=1400kg x 2 m/s/s
Force=2800N
Increasing Acceleration: increase the force OR decrease the mass.
If force is constant, an increase in mass causes a decrease in acceleration.
A decrease in masses causes an increase in acceleration.
We know that objects with different masses accelerate to the
ground at the same rate.
This means they will hit the ground at the same time…
BUT, because of the 2nd Law we know that they don’t hit the
ground with the same force.
F = ma
F = ma
98 N = 10 kg x 9.8 m/s/s
9.8 N = 1 kg x 9.8 m/s/s
3rd Law of Motion
If one object exerts a force on another object, then the second object exerts a
force of equal strength in the opposite direction on the first object.
** For every action, there is an equal and opposite reaction**
Momentum
Product of mass and velocity
Momentum= mass x velocity
Unit: kg x m/s
Law of Conservation of Momentum: In the absence of outside forces, the total momentum of objects that
interact DOES NOT CHANGE
 What outside forces?!?--Gravity and FRICTION!!!
Conserving Momentum: In the absence of outside forces, the total momentum of objects that interact DOES
NOT CHANGE
Transferring Momentum: (type of conserving) Momentum can be transferred from one object to another
4m/s
2m/s
4m/s
2m/s