What makes inertia?

Main Question or Discussion Point

What makes an object overcome inertia so that it accelerates in terms of changing direction? I know friction decelerates the object, but I cannot figure out if it is center of gravity or centripetal force that changes direction by overcoming the object's inertia. Also, what is the big difference between inertia and friction itself?

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Astronuc
Staff Emeritus
The classic definition of inertia is - The tendency of a body to resist acceleration; the tendency of a body at rest to remain at rest or of a body in straight line motion to stay in motion in a straight line unless acted on by an outside force.

Inertia is a property of matter (it mass). Mass resists acceleration. Acceleration is achieved by imposing a force on matter. The acceleration is given by a = F/m.

Friction is an opposing force to motion be it solid against solid or fluid (air or liquid) against solid. A body transfers momentum to the objects or material it encounters.

The center of mass is the mean position of the matter in a body.

Doc Al
Mentor
modeman said:
What makes an object overcome inertia so that it accelerates in terms of changing direction?
All forces accelerate an object, in the sense of changing the object's velocity: its speed or direction. Forces that acts sideways to the object's direction of motion will change that direction without changing the speed.

For example, a car driving around a circular track at constant speed requires a centripetal force to keep it going in a circle. If the road is flat, friction provides that force. That friction force acts sideways to the car's direction at all times.