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1. Feb 16, 2017

### Ricardeo Xavier

1. The problem statement, all variables and given/known data
This is the problem
http://imgur.com/a/1XFlt

2. Relevant equations

This is the given FBD
http://imgur.com/a/CURqA

3. The attempt at a solution

Now the car should have a tendency to slip down the ramp thus causing the frictional force to oppose this motion. But the frictional force is pointed down the ramp in this worked out problem. Can someone explain to me why this is?

2. Feb 16, 2017

### Ricardeo Xavier

Why is friction pointed down the ramp? Shouldnt it be pointed up the ramp?

3. Feb 16, 2017

### Staff: Mentor

If there were no ramp (i.e. the ground was flat) and the car was going around a curve, what direction would the friction force have to point?

4. Feb 16, 2017

### Staff: Mentor

Note that they ask for minimum and maximum speeds. What happens when you take the curve too fast? Which direction do you tend to slip?

5. Feb 16, 2017

### kuruman

First draw the FBD to determine how fast the car must be moving if there were no friction, i.e. sliding around a frictionless curve.
If the car is moving faster than that, friction down the incline is needed to keep it in a horizontal circle.
If the car is moving slower than that, friction up the incline is needed to keep it in a horizontal circle.

6. Feb 16, 2017

### Ricardeo Xavier

Thanks everyone for the great responses! It really helped clarify things for me (: