# When does slipping occur?

1. Oct 2, 2010

### candymountain

So im trying to figure out under what circumstances slipping usually occur, and what causes it to occur.

lets assume we have a cart, and there is a static friction mu between the surface and the wheel.

let's say the cart is being pushed at F horitonztally. Fs, force of friction, obviously opposes the motion.

So my question is, when does skipping occur?

is it when l F - Fs l <= Fs ? Also what causes slipping? is it too much torque supplied? are there any other cases in which slipping can occur?

thanks a lot :)

candy~

2. Oct 3, 2010

### Idoubt

I'm not sure I understand exactly what you said ( what's |F-Fs| <=Fs)

But I would think slipping occurs when Fhorizontal > Ffriction

Ie the ground cannot stop your relative motion.
Since you need relative motion at the point to stop for rolling ( and walking incidentally) rolling doesn't occur

3. Oct 3, 2010

### lj19

Slipping could occur when the force exerted on the floor with the wheels is greater than the force of friction. [The applied force is greater than frictional force.] That would could friction to decrease.

4. Oct 3, 2010

### candymountain

wouldn't that mean the object would accelerate? i'm really confused

5. Oct 3, 2010

### lj19

It could decelerate or accelerate, which is it slowing down at an increasing speed, or increasing at an increasing speed, but it depends on the amount of frictional force versus the amount of applied force.

6. Oct 3, 2010

### candymountain

..... then how does it slip..?

7. Oct 3, 2010

### lj19

Is this object on an inclined plane or on a flat surface?
If it is on an inclined plane then it depends on the amount of frictional force versus the applied force. If the applied force pushing it down the inclined plane is greater than the frictional force trying to not push it down, it will "slip".

8. Oct 3, 2010

### candymountain

in my case i have a car going on a flat surface for few meters, then goes up a ramp.

does slipping occur when it rolls down(when it tries to go up)? i.e. friction force > F applied?

9. Oct 3, 2010

### lj19

Does the car keep a constant speed?
Slipping on the ramp [inclined plane] would occur when the force applied is less than the force of friction.

10. Oct 3, 2010

### candymountain

well there's a constant force aplied to the car, so its accelerating.

oh okay, so how does the flat surface slipping works

11. Oct 3, 2010

### lj19

Well a car cannot be constant and accelerate at the same time. If there is a constant force being applied before it goes up the ramp, it could change when it reaches the ramp and goes up. To have a constant force going up the ramp, or on a flat surface, the force applied [pushing the car] would have to be equal to the force of friction. If the force of friction is greater than the force applied then the car would decelerate [slow down at an increasing speed] or slow down at a constant speed. If the force applied is greater then the car would accelerate [speed up at an increasing speed], or speed up at a constant speed.