# Homework Help: Work and Power Questions NEED Help

1. Jan 21, 2008

### Turnips

1. A 50kg crate is pulled 40m along a horizontal floor by a constant force exerted by a person, Fp=100N, which acts at a 37 degree angle. The floor is rough and exerts a friction force Ff= 50N. Determine the work done by each force acting on the crate (including normal force and force of weight), and the net work done on the crate.

W=F*d*cos( angle )

3. no idea how to do it.

2. Jan 21, 2008

### rock.freak667

What is the magnitude of the component of Fp acting in the direction of motion?

3. Jan 21, 2008

### Turnips

Im guessing its just 100N because thats all the problem gives me.

4. Jan 21, 2008

### rock.freak667

Are you familiar with http://www.glenbrook.k12.il.us/gbssci/phys/Class/vectors/u3l3b.html [Broken]?

Last edited by a moderator: May 3, 2017
5. Jan 21, 2008

### Turnips

Yes.

6. Jan 21, 2008

### rock.freak667

Then resolve the 100N acting at 37 degrees into horizontal and vertical components.

7. Jan 21, 2008

### Turnips

The Fy = 60.18N and the Fx = 79.86N

8. Jan 21, 2008

### rock.freak667

Good.

Now what would be the work done in moving the crate 40 m in the direction of Fx? and in the same manner what is the work done by the frictional force?

9. Jan 21, 2008

### Turnips

79.86N * 40 m = 3194.4J is the Work done in the x Direction
50N * 40m = 2000J is the work done by Friction

10. Jan 21, 2008

### rock.freak667

That is what the question asks for.

Now vertically. Is the crate moving either up or down? If so then some force is doing work on it. If not then no work is done on the crate

11. Jan 21, 2008

### Turnips

Alright thanks very much.