# Homework Help: Block sliding down an inclined plane

1. Jun 8, 2014

### Seahawks

1. The problem statement, all variables and given/known data

A block takes 3 times as long to slide down an inclined plane that makes an angle of 30 degrees as it does to fall freely through the same vertical distance. Determine the coefficient of friction.

2. Relevant equations

F=μN

3. The attempt at a solution

I do not know where to start.

2. Jun 8, 2014

### 2milehi

Now throw in some kinematic equations.

3. Jun 8, 2014

### Seahawks

vf=vi+at
vf^2=vi^2+2as
d=vit+.5at^2

Now how do i solve this problem

4. Jun 8, 2014

### 2milehi

Now Newton's second and free body diagram. Also ignore air friction.

5. Jun 8, 2014

### Nathanael

How long does it take a block to fall a distance x freely?

How long does it take a block to slide a distance y down a 30 degree slope? (With friction)

What should the distance y be to make the vertical distance equal to x?

What does the coefficient of static friction need to be to make the time take 3 times as long on the slope?

6. Jun 8, 2014

### Nathanael

The problem you asked can be a bit tricky. Try solving this problem first:
(You should be able to solve this problem before you can solve the one you asked:)

How many times longer does it take a block to move a vertical distance down while sliding down a frictionless inclined plane that makes an angle of 30 degrees (with the horizontal) than it takes to move the same vertical distance when falling freely?

(I don't know if I worded that question clearly, but it's basically the same problem except I told you that the coefficient of friction is zero, and I am asking you how many times longer does it take)

7. Jun 17, 2014

### 2milehi

Seahawks - have you made an attempt at this problem?

8. Jun 17, 2014

### Staff: Mentor

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