#### 12.2 + 12.3 Newton's Three Laws of Motion and Momentum

Newton's First Law (law of inertia)

the state of motion of an object does not change as long as the net force acting on the object is zero

inertia

the tendency of an object to resist a change in its motion
ex: an object in rest tends to remain in rest, and an object in motion tends to stay in motion

mass

the measure of the inertia of an object and depends on the amount of matter the object contains

Newton's Second Law

the acceleration of an object is equal to the net force acting on it divided by the object's mass (a=F/m) N/kg = m/s2

weight

the force of gravity acting on an object, and is the product of the object's mass and acceleration due to gravity (W=mg) (g= 9.8 m/s2)

Mass vs. Weight

Mass is a measure of the inertia of an object; weight is a measure of the force of gravity acting on an object.

Newton's Third Law

Whenever one object exerts afford on a second object, the second object exerts an equal and opposite force on on the first object, and don't balance

reaction force

force exerted by second object

action force

force exerted by first object

momentum

the product of an object's mass and its velocity

Momentum Formula

Momentum= mass X velocity

Mass vs. Velocity in Momentum

An object has a large momentum if the product of its mass and velocity is large.

law of conservation of momentum

if no net force acts on a system, then the total momentum of the system does not change

In a Closed System

In a closed system, the loss of momentum of one object equals the gain in momentum of another object momentum is conserved.

action-reaciton pairs

one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object