# Object on an incline plane

1. Sep 28, 2010

### pb23me

1. The problem statement, all variables and g
object on an incline plane has a mass of 10 kgs and the coefficient of static friction is 0.35 at what angle does the object begin to slide.

2. Relevant equations
Fnet=ma Ff=sin(theta)(mg)

3. The attempt at a solution I dont come close to the solution because i feel as though some piece of information is missing. Therefore i cant begin to solve the problem.

2. Sep 28, 2010

### Staff: Mentor

What's the maximum value of static friction for a given angle?

3. Sep 28, 2010

### pb23me

isnt it Fn(Us) or normal force times static friction?

4. Sep 28, 2010

### pb23me

not actuallu u that symbol that looks like a u the micro symbol

5. Sep 28, 2010

### pb23me

so the normal force is equal to (mg) or in this case (10kg)*(9.86) oh ok i think ive got it now thank you very much...

6. Sep 28, 2010

### Staff: Mentor

The maximum value for static friction equals μFn.

Careful! The normal force does not equal mg. (It would if the surface were horizontal, but it's not.) Hint: Find the component of the weight perpendicular to the surface.

7. Sep 28, 2010

### pb23me

cos(theta)*mg

8. Sep 28, 2010

### Staff: Mentor

Good!

So what's the maximum static friction force?

9. Sep 28, 2010

### pb23me

(.35)*cos(theta)*mg

10. Sep 28, 2010

### Staff: Mentor

Good.

So what's the condition for the object to just barely start to slide?

11. Sep 28, 2010

### pb23me

is this correct???

12. Sep 28, 2010

### pb23me

sin(theta)mg be greater than (.35)*cos(theta)*mg

13. Sep 28, 2010

### Staff: Mentor

Yes. But to solve for the point where the object is just about to slide, set them equal. That will be the critical angle.

14. Sep 28, 2010

### pb23me

ok i got tan(theta)=.35 inverse tan(.35)= 19.3 deg

15. Sep 28, 2010

### Staff: Mentor

Sounds good to me.

16. Sep 28, 2010

### pb23me

awsome thank you soooo much!