Warm - Up The rate of change of velocity is known as:

A. momentum.

B. speed.

C. acceleration. What is force?

A push or pull that usually causes a change in an objects motion.

7-2 – Newton’s 1st

Describe Newton’s first law of motion and its relation to inertia.

Mass & Inertia Inertia is the resistance an object has to a change

in its state of motion. Mass has an affect on inertia. Mass is directly proportional to inertia. An object that has a greater mass has a greater

tendency to maintain its state of motion. Increased mass, increased inertia.

Which has more inertia?Basketball or golf ballPencil or textbookEarth or you

If friction could be eliminated

Newton’s 1st Law The 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. Objects at rest stay at rest; Objects in motion stay in constant straight-

line motion.Unless acted on by an outside force.

Forces in action Seat belts work using

inertia. In a head-on collision,

your body wants to stay in motion.

The seat belt keeps you from continuing to travel.

Check your understanding? Suppose that an astronaut in that space throws a

rock. The rock will

a) gradually stop.

b) continue in motion in the same direction at constant speed.

Mac and Tosh are arguing in the cafeteria. Mac says that if he flings the Jell-O with a greater speed it will have a greater inertia. Tosh argues that inertia does not depend upon speed, but rather upon mass. Who do you agree with? Explain why.