# Net work problem with F cos theta

1. Oct 29, 2010

### loganblacke

1. The problem statement, all variables and given/known data
The graph below shows the component (Fcos(theta)) of the net force that acts on a 5.0 kg block as it moves along a flat horizontal surface. Find (a) the net work done on the block and (b) the final speed of the block if it starts from rest at s = 0.

The graph shows Fcos(theta)(N) as the y-axis and s (meters) as the x-axis. The coordinates are (0,0), (1,0), (1,2), (4,2), (4,-2), (6,-2), (6,0), (8,0), connected by straight lines in that order.

2. Relevant equations

Work=Force*Distance*cos(theta)

3. The attempt at a solution

I don't understand what the y value represents or what values to assign for theta. Please help!

2. Oct 29, 2010

### paragchitnis

Work = Force x cos$$\Theta$$ x distance
This is the area under the given graph between Fcos$$\Theta$$ and s

3. Oct 29, 2010

### paragchitnis

Fcos$$\Theta$$ is the force acting in the direction of the motion of the body.
The acceleration of the body in the direction of motion can be calculated as
Force = mass x acceleration
After finding acceleration use
vf2 = vi2 + 2ax

Last edited: Oct 29, 2010
4. Oct 29, 2010

### loganblacke

A=.25/5.0=.05 m/s

Vf=sqrt(2*.05*8)=.8944 m/s^2