Changing an object's state of motion requires an outside force.
Newton's 1st Law is sometimes called the law of inertia. (Credit to @Nancy F. See https://socratic.org/physics/forces-and-newtons-laws/newtons-first-law)
Newton 1st Law is often stated "An object at rest tends to remain at rest unless acted on by an outside force and an object in motion tends to continue in motion, in a straight line, unless acted on by an outside force." Those are the characteristics of inertia.
Another way to describe it is to say that the inertia of an object makes it unwilling to change its state of motion. An outside force is necessary to cause a change in state of motion.
- Try kicking a bowling ball. It will not move the way a football would. That is because it has more inertia. It is hard to convince it to move.
- When a bowling ball hits the bowling pins, it apparently slows down only slightly, if at all.
- When riding in a car or bus that is turning, your body tends to continue moving in the original direction.
- A car or bus slows only gradually when the driver takes foot of the gas.
- Inertia is the reason that wearing seat belts when in a car is a good idea. When the car stops suddenly, you may not stop until your nose hits the windshield.
I hope this helps,