Net work problem with F cos theta


by loganblacke
Tags: theta, work
loganblacke
loganblacke is offline
#1
Oct29-10, 10:41 AM
P: 48
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!
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paragchitnis
paragchitnis is offline
#2
Oct29-10, 11:01 AM
P: 25
Work = Force x cos[tex]\Theta[/tex] x distance
This is the area under the given graph between Fcos[tex]\Theta[/tex] and s
paragchitnis
paragchitnis is offline
#3
Oct29-10, 11:16 AM
P: 25
Fcos[tex]\Theta[/tex] 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

loganblacke
loganblacke is offline
#4
Oct29-10, 12:36 PM
P: 48

Net work problem with F cos theta


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

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

Thank you for your help!!!
paragchitnis
paragchitnis is offline
#5
Oct30-10, 09:51 AM
P: 25
Thank you for giving new problem to me.
Is the answer correct?


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