# Work and Force on a block of mass

1. Jan 29, 2007

### chamonix

1. The problem statement, all variables and given/known data
A 5.0 kg block is pushed 3.0 meters at a constant velocity up a vertical wall by a constant florce applied at an angle of 30.0 degrees witht the horizontal. If the coefficient of kinetic friction between the block and the wall is 0.30, determine the following:
a) the work done by the force on the block
b) the work done by gravity on the block
c) the magnitude of the normal force between the block and the wall

2. Relevant equations
W=Fdcosø
W=mgh
Fn=mgcosø

3. The attempt at a solution
W=Fdcosø
W=mu*mgdcosø
W=.3*5*9.81*3*cos30
W=38.23J

w=mgh
w=5*9.81*3

fn=mg
fn=5*9.81*cos30
fn=42.48

I have a feeling that this is wrong. Any help would be most appreciated. Thanks.

2. Jan 29, 2007

### PhanthomJay

You should first draw a free body diagram of the block, and identify all the forces acting on the block. In particular, the Normal force is the force the wall exerts on the block, perpendicular to it. In this problem, the Normal force has nothing to do with the block's weight. Then use Newton 1 before attempting a solution to the work done by the force.

3. Jan 29, 2007

### chamonix

Thank you. I will try this.
So, would my equations for the problems be correct?

Last edited: Jan 29, 2007