# Homework Help: Inertial and static friction?

1. Sep 6, 2009

### semc

HI guys, i was wondering what is the difference between inertial and static friction? If a car is on a frictionless ground, does it have static friction and the inertial is the same even if it is on a rough surface right?

2. Sep 6, 2009

### Staff: Mentor

What do you mean by "inertial" friction? Are you thinking of kinetic friction?
If the ground is frictionless, how can there be static friction?

3. Sep 6, 2009

### semc

erm nope i am talking about inertial of a mass.

4. Sep 6, 2009

### kuruman

What is your understanding of what "inertial of a mass" is? I am not sure what you mean by this term.

5. Sep 6, 2009

### semc

Actually i meant inertial an i believe inertial is the resistance of mass to a change of its state of motion.Am i right?

6. Sep 6, 2009

### Staff: Mentor

I think you mean inertia, which is measured by mass. If so, can you restate your question, as I don't understand how that relates to friction.

7. Sep 6, 2009

### semc

Sorry about that, i meant to ask whether inertia changes if the surface is frictionless

8. Sep 6, 2009

### Staff: Mentor

"Inertia" is a property of a body due to its mass. Why would it change?

9. Sep 6, 2009

### semc

yeah that was what i though. so when force is applied to an object, the force only have to exceed the static force in order for it to move right? What about inertia?

10. Sep 6, 2009

### Staff: Mentor

Right. If you are trying to push a box along a rough horizontal surface, then to start it moving you must push with a force that exceeds the maximum static friction between the box and the surface.

Perhaps you are thinking of how much force is required to get something moving if there is no friction? What do you think? If that box is on a frictionless surface, how hard do you have to push it to start it moving?

11. Sep 6, 2009

### semc

If there is no friction that means the object will move and continue its state of motion even if the force is very little?

12. Sep 6, 2009

### Staff: Mentor

Right! From Newton's 2nd law, if you apply a net force F, the mass will have an acceleration = F/m. The harder you push, the greater the acceleration, but even the slightest push will create some acceleration.