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Net work problem with F cos theta

  1. Oct 29, 2010 #1
    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


    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. jcsd
  3. Oct 29, 2010 #2
    Work = Force x cos[tex]\Theta[/tex] x distance
    This is the area under the given graph between Fcos[tex]\Theta[/tex] and s
  4. Oct 29, 2010 #3
    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
    Last edited: Oct 29, 2010
  5. Oct 29, 2010 #4
    A=.25/5.0=.05 m/s

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

    Thank you for your help!!!
  6. Oct 30, 2010 #5
    Thank you for giving new problem to me.:smile:
    Is the answer correct?
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