# Is inertia present in a body while in state of motion?

According to Newton's law of inertia (written in book:The Mathematical Principles of Natural Philosophy**) it is said that in all objects having mass, have always inertia included in their property but if a body is in motion well then, would there be inertia in that body.

For instance: A ball is hit by a bat and is in state of motion in air so would there be inertia present in that current state of ball or not?

According to friction law of physics friction is any thing which exists when two or more bodies come in contact with one-another and it is against the direction of force (pushing a body) which is against inertia so would friction be helpful too in supporting inertia of a body consequently?

If yes then could it be said that, inertia is directly proportional to the friction?

• Of course. There is static inertia, in a stationary body, measured by its mass. And the other kind is dynamic inertia, measured by the momentum of the body. p=mv – Self-Made Man Sep 15 '13 at 1:33
• Sounds like you got it man.thank you!Can you tell me one more thing that how would we calculate inertia in statics and dynamics both? – Sufyan Shaikh Sep 16 '13 at 17:37
• Also you have not answered me that whether i am right about relation of friction and inertia or not? – Sufyan Shaikh Sep 16 '13 at 17:55

Friction is a force acting between to bodies against their "relative" motion (to understand the term "relative", see how friction can sometimes increase the velocity of a body in a given frame.) And then you said, "which is against inertia so would friction be helpful too in supporting inertia of a body consequently." I am not what you want to say here but I think this is not a correct statement. Inertia is a property not a force. And $F = \frac{\mathrm{d}(mv)}{\mathrm{d}t}$, rate of change of momentum with time. Now you can see that if force is same and we have a heavier mass and a lighter constant mass, change in velocity ($a = \frac{F}m$) will be less in case of heavier mass. So we can say that heavier mass has more inertia than the lighter mass.