Learn: Newton's First Law of Motion - Inertia

friction

the force that acts between materials as they move past each other

inertia

the property of a body to resist changes to its state of motion

When is a force needed to keep an object in motion?

A force is needed to keep an object in motion when friction is present.

Newton's first law (the law of inertia)

Newton's first law states that every object continues in a state of rest, or in a uniform speed in a straight line, unless acted on by a nonzero net force.

mass

the quantity of matter in an object

mass is measured in...

kilograms

weight

the force of gravity on an object

What is the relationship between mass and inertia?

The more mass an object has, the greater its inertia and the more force it takes to change its state of motion.

How does the law of inertia apply to objects in motion?

The law of inertia states that objects in motion stay in motion if no unbalanced forces act on them.