What causes motion?

Sir Issac Newton

1642-1727 Developed laws of motion by age 24.

Newton’s 1st Law of Motion

Law of InertiaA body at rest, stays at rest; a body in motion stays in motion until an outside force acts upon it.

Inertia

Tendency of an object at rest to stay at rest, or an object in motion to stay in motion.

Inertia All objects resist

changes in motion. All objects have

mass, therefore they have inertia.

An object with a small mass can be accelerated with a small force.

Mass is a measure of inertia.

Newton’s 2nd Law of Motion The acceleration of an object is

directly proportional to the force acted upon the object and inversely proportional to the mass of the object.

Newton’s 2nd Law of Motion If the Force increases, the

acceleration of the object increases. If the mass is increased, the

acceleration of the object decreases.

a=F/m

What is the acceleration of a 132 kg object being moved with a 268 N force? m=132 kg F=268 N a=F/m a=268 N/132 kg a=2.03 m/s2

Weight

Force of gravity on an object

Mass X Gravity (freefall acceleration)

W = mg

What is the weight of Mark on Earth if his mass is 72-kg? m=72 kg a=9.8 m/s2

W=mg W= (72 kg)(9.8 m/s2) W=710 N

Newton’s 3rd Law of Motion

For every action, there is an equal and opposite reaction.

Law of Action and Reaction

Action-Reaction Forces always

occur in pairs. Whenever a force

is exerted, another force occurs that is equal in size an opposite in direction.