1. Feb 27, 2007

### future_vet

1. The problem statement, all variables and given/known data
When you sit on a chair, the resultant force on you is ..?
3. The attempt at a solution
Down, because of gravity?

1. The problem statement, all variables and given/known data
In the absence of an external force, a moving object will:
stop immediately
slow down and eventually come to a stop MY ANSWER
go faster and faster
move with constant velocity

1. The problem statement, all variables and given/known data
An object is placed on an inclined plane. The angle of the incline is gradually increased until the object begins to slide. The angle at which this occurs is theta. What is the coefficient of static friction between the object and the plane?
2. Relevant equations
tan(theta)
That's what I understood, but I need to make sure...

Thanks!

2. Feb 27, 2007

### nealh149

All of your answers are incorrect. Try again, draw force diagrams and really think these problems through.

3. Feb 27, 2007

### future_vet

For the first one, the force on the chair is down, but the force on me is up... Would this be correct?

4. Feb 27, 2007

### future_vet

For the second one, I reviewed the laws, and I would say that the velocity would stay constant (unless some external force came into play). Would this be correct?

5. Feb 27, 2007

### Staff: Mentor

EDIT -- And I believe that your answer for the 3rd one is correct, $$\mu_s = tan( \Theta )$$

Last edited: Feb 27, 2007
6. Feb 27, 2007

### future_vet

Are you absolutely sure my last answer is incorrect?...

The Prenhall website has the same question. I entered an answer other than tan to make sure, and I got:
An object is placed on an inclined plane. The angle of incline is gradually increased until the object begins to slide. The angle at which this occurs is θ. What is the coefficient of static friction between the object and the plane?

sin θ

tan θ

7. Feb 27, 2007

### future_vet

You mean that if F doesn't change, and m doesn't change, a will be constant?

8. Feb 27, 2007

### Staff: Mentor

That is correct.

9. Feb 27, 2007

### Staff: Mentor

No, I mean that if there is no external force, the acceleration is zero. And you correctly inferred that this means the velocity is constant.

10. Feb 27, 2007

### future_vet

Thank you!

11. Mar 8, 2009

### hiteshjain16

the resultant force on me is mg upward where m is my mass angd is acceleration due to gravity

12. Mar 8, 2009

### hiteshjain16

in absence of external force body moves with constant velocity