# Homework Help: Frictional Force and acceleration

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1. Oct 20, 2014

### karajo

The problem statement, all variables and given/known data

The force applied to a cart is 10.5 N. The cart now moves toward the right at an acceleration also toward the right of 1.75m/s2. What are the magnitude and direction of the frictional force?

The attempt at a solution
I found that my mass is 6kg. I have F, m, and a, but I am unsure how to find the frictional force.

2. Oct 20, 2014

### Staff: Mentor

What forces act on the cart? Draw yourself a free body diagram, then apply Newton's 2nd law.

3. Oct 20, 2014

### Staff: Mentor

How did you determine the mass? I assume is was given elsewhere in the problem?

4. Oct 21, 2014

### karajo

I found mass by using F=ma
Force=10.5N
acceleration=1.75m/s2

I drew a free body diagram with Force in the positive direction, friction pulling the negative way, and acceleration in the positive direction. Also the Normal force going up and mass*gravity going down.

5. Oct 21, 2014

### Staff: Mentor

That won't work. For one thing, Newton's 2nd law should be written as $\Sigma F = ma$, where $\Sigma F$ stands for the net force. In this problem, all you know are the applied force and resulting acceleration.

You need to be given the mass; there's not enough information to figure it out. Make sure you've posted the full problem, exactly as it was given.
Good.

6. Oct 21, 2014

### karajo

Oh, I have a mass of 3.23 kg for the cart.

7. Oct 21, 2014

### Staff: Mentor

That makes more sense. Now you can figure out the net force.