Law of Inertia

Every object in a state of uniform motion tends to remain in that state of motion unless an unbalanced force is applied to it.

An object at rest An object in motion

Friction is the force that acts on a moving object to slow it down and bring it to stop.

Question 1: Evaluate the following assertion.

If there is no frictional force on the road, cars can move without consumption of energy by the Newton’s first law of motion. So we can save energy.

A dynamic cart with a brick on it. Get it moving and stopped. Tape the brick to the cart. Get it moving and stopped again. Seat belts protect us from being hurt by

keeping us tied to the vehicle.

The resistance an object has to a change in its state of motion.

Question 2: What does the magnitude of inertial force depend on?

F = ma m: inertial mass

Opening a bottle Removing dusts from cloths Seat belts Seismometer

Seat belts can exert forces to cause passengers to slow down at the same rate as the vehicle.