# Finding the Force

1. Mar 9, 2013

### science_again

What force is required to pull a 150-pound sled along a horizontal surface? The coefficient of friction is 0.10 and the sled is pulled by a rope which makes an angle of 30 degrees with the horizontal?

2. Mar 9, 2013

### ap123

Hello science_again

What have you done to solve this problem?
Have you drawn a free-body diagram for the sled.

3. Mar 9, 2013

### science_again

This is where I am at.

F cos 30 - 0.10(friction) = 0
F cos 30 = 0.10 x normal force (Fn) [1]
Fn + F sin 30 - weight of sled = 0 [2]

Therefore substitute, put [2] in [1] you get 0.866F = 0.1(weight of sled - 0.5F)

should the weight of sled convert to kg?

4. Mar 9, 2013

### lep11

You don't need to.

Last edited: Mar 9, 2013
5. Mar 9, 2013

### ap123

That looks correct.
Try and work out F using symbols and then substitute the numbers at the end of the problem.
This makes it easier to avoid errors.

Normally you would use the same units that the question uses, so pounds would be ok.

6. Mar 9, 2013

Thanks