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Homework Help: Find the work done on the car by a string

  1. Oct 17, 2007 #1
    Ok, so I'm doing a lab. A car is attached to a mass by a string. The car sits on an inclined ramp. At the end of the ramp theres a pulley where the hanging mass is hangs from.

    I collected the following date:

    the mass of the car is .5 kg
    the mass of the hanging mass if .055 kg
    the angle of incline is 3.47 degrees
    the car's acceleration up the ramp is .587 m/s^2
    the length of the ramp up which the car travels is .651 m

    I want to find the work done on the car using this data.

    Perhaps I can use W=Fdcosx ? I DON'T KNOW! I need help because when I do m,total*acc*d*cos x , i dont think this is right

    i calculated the work done on the car another way, by using W=change in potential energy.

    its change in vertical height up the ramp is .02 m ... so the work would be m,car*g*change in height = -.098J

    RIGHTT?? but i need to use the other way..
  2. jcsd
  3. Oct 17, 2007 #2
    also in this same lab i need to find effort force and resistance force!? I DON'T EVEN KNOW WHAT THOSE ARE.
  4. Oct 18, 2007 #3

    Shooting Star

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    Homework Helper

    There is possibly friction between the car and the plane, which is the resistant force. Confirm this with your teacher. If that is so, the following should give you enough hint to go on.

    1. Find the speed of the car when it reaches the topmost point. You can do it because you know the accn. Then you have the final KE of the car.
    2. The hanging mass and the car have the same speed since they are tied together. So, you have the final KE of the hanging mass.
    3. They have travelled the same distance.
    4. Now think where the difference of the initial total E and the final total E has gone. (Remember to include both bodies, not just the hanging mass.)
    5. Find the resistant force.
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