# Inertia of a mass in vacuum of space

1. Sep 7, 2008

### Gear300

A thought just sort of popped out presenting a question I'm not sure I've ever answered:

An object is in free space with no friction present throughout the surroundings. A person is placed near the object and decides to push the object away from him/her. There is no friction present. What I'm wondering is if the object immediately moves when the force is applied. If the object has a mass and hence, inertia, shouldn't there be some sort of time lag before it started to move?

2. Sep 7, 2008

### Chi Meson

Re: Inertia

If there is no friction at all, then as soon as a force is applied to any object it begins to accelerate (according to Newton's 2nd Law), which means it's motion changes immediately.

In all cases of contact forces between two objects, the net force on one object is not constant; it begins as infinitesimally small and proceeds quickly to a maximum, then trails off to zero again. So all accelerations begin as infinitesimally small. Depending on the nature of the contact and the masses of the objects, this initial acceleration may or may not be observable. If it is, then it might appear that the object does not accelerate at first, when in fact the acceleration is there, but too small to observe.

3. Sep 7, 2008

### Gear300

Re: Inertia

I see, I see...so is inertia is something characteristic of how long it takes applied energy to distribute across a mass?

Last edited: Sep 7, 2008