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Mechanics Question of a wheel chair

  1. Apr 9, 2004 #1
    A person in a wheel chair is moving up a ramp at a constant speed. Their total weight is 900N. The ramp makes an angle of 10degrees to the horizon.
    Calculate the force required to keep the wheel chair moving at constant speed up the ramp.
    (You may ignore the effects of friction)

    The ramp is 5m long. Calculate the power exerted by the person in the wheel chair if it takes her 10s to travel up the ramp.

    Here is what i have done :confused:

    - I used the SINE Rule to find the inclined height of the ramp, i found it to be .87m.

    - Power = work/time.
     
  2. jcsd
  3. Apr 9, 2004 #2

    Doc Al

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    Staff: Mentor

    Start by finding the force needed to move the chair at constant speed up the ramp. Hint: Constant speed up the ramp means equilibrium. What are all the forces acting on the chair?
     
  4. Apr 15, 2004 #3
    I still dont understand how to find the constant speed up the ramp??

    All the forcesacting on the chair are gravity, friction (but friction is to be ignored). Is that it?
     
  5. Apr 15, 2004 #4

    Doc Al

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    Staff: Mentor

    If you want to find the speed you need distance and time. You are given both. (But you don't need to find the speed.)
    The forces acting on the chair are: gravity pulling down, the normal force of the ramp pushing on the chair, and the applied force pushing the chair up the ramp.

    Consider the components acting parallel to the ramp: The applied force (F) pushing up the ramp, and the component of weight acting down the ramp (mg sinθ). These must balance for the chair to have constant speed.
     
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