An example of inertia could be when you are in a car and it stops. You know how your body suddenly jumps forward? That's inertia. Inertia is the tendency of a body to resist a change in motion or rest. In the same way, you jump backward when the car starts moving forward. So if you tried to play soccer or baseball without inertia, it would be difficult to score a goal or home run as the ball would try to resist changing direction.
