Newton’s 1st Law

• (1642 – 1727)- English Scientist who developed the 3 Laws of Motion which explains:• Objects at rest• Constant motion• Accelerated motion• Balanced and unbalance forces & how

they cause these states of motion

Sir Isaac Newton

• Newton’s 1st Law: an object at rest will remain at rest, and an object is motion will remain in motion at a constant velocity unless an unbalanced force acts upon it.

• Also known as the Law of Inertia

Newton’s 1st Law of MOtion

• Force is a push or a pull that affects matter. Forces can start, stop, accelerate, or change directions of an objects motion– Force is measured in Newtons– So if it is unbalanced then that

means one forces is greater than another force acting on the same object

What are Forces

Gravity as an unbalanced force

• If gravity is the unbalanced force on an object the object is said to be in Free Fall

• So why are we not always in free fall?

• When we stand on the ground gravity’s force pulls us down and the floor’s force pushes up

Inertia• Inertia- This is the tendency of objects to remain in

motion or to stay at rest• In short it means an objects resistance to change its

state of motion

Examples:1. Car accident- Seat Belts2. Book on a desk3. Roller skating4. Roller coaster turning

More Inertia

• Is the inertia the same for a fly as a train?– No the train has more inertia– BECAUSE the train has more mass

• The more mass you have the more inertia you have

This is different from momentum. An object at rest has no momentum but it does have inertia.

Circular Motion

• Centripetal acceleration- the acceleration of an object moving in a curved path or circle.

• Centripetal force- the force that causes an object moving at a constant speed to move in a curved path or circle.