Answer:
Step-by-step explanation:
Newton's First Law:
" The observation that objects in motion tend to stay in motion, and objects at rest tend to stay at rest unless an outside force acts upon them. "
Newton's first law is that if the net force acting on an object is zero, that the object's velocity remains constant.
The easy way to think of it is like this:
Unless acted on by an unbalanced external force, an object in motion will remain in motion, and an object at rest will remain at rest.
If you imagine a soccer ball sitting still on the ground, it's not going to go anywhere. But if someone comes along and kicks it, they are applying an external force, and now the ball is going to go somewhere. As it rolls along the field, friction starts to act on it (both in the form of wind resistance, and friction between the ball and the field,) which will slow it down, until it stops.
Inertia is the tendency of a body to resist changes to its velocity. The more mass something has, the more inertia it has. If you stand still on a stationary bus, without holding the handrail, you'll be thrown off balance when the bus starts moving. Because your body wants to stay at rest, so it briefly resists the change in velocity brought on when the bus starts moving.