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What can be calculated from a trolly rolling down an inclined plane?

  1. Dec 12, 2008 #1
    1. The problem statement, all variables and given/known data

    Not a problem but an experiment were I have not been told what I need to calculate.

    I have a trolley rolling down an inclined plane. We recorded the speed(light gates) at two different points and all distances involved(height of plane, distance between gates etc). We did not record the mass of the trolley.

    So far I think I can calculate
    acceleration of the trolley using a = (v^2 -u^2)/(2*s)
    acceleration due to gravity(approx) using a = g sinѳ

    Does this seem correct? Is there any thing else I can work out from the information I have? What if I could get the mass of the trolley? I am just unsure about what else I should be looking for.

    It would be great if someone could point me in the right direction.

    Thanks
     
  2. jcsd
  3. Dec 12, 2008 #2

    PhanthomJay

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    What is the difference between the 'acceleration of the trolley' that you calculate using the kinematic equation based on your measurement of v, and the 'aceleration due to gravity = (approx) g sin theta'?
     
  4. Dec 13, 2008 #3
    Sorry, that wasn't very clear. I found g using g=a/sinѳ
     
  5. Dec 13, 2008 #4

    PhanthomJay

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    That's what i mean. If you divide your calculted "a" by sin theta, you should, in the ideal case without friction or air drag, get a value of 'g' of 9.8m/sec^2 or 32ft/sec^2, depending on what system of measure and units you are using. How close does your calculated value of 'a' compare to the theoretical value of 'g sin theta'? If they are not the same, how do you explain why they are not the same?
     
  6. Dec 15, 2008 #5
    My values are off by about 2-3m/sec^2 with the difference decreaseing as the angle of the plane increases. This is down to friction(air and wheels).

    Is it possible to work out the coefficent of friction if I had the mass? I know all the other values so I can work out the difference between my recorded values and the results i would get if there was no friction or air resistance. And would the coefficient change as the angle of the slope was changed?
     
  7. Dec 15, 2008 #6

    PhanthomJay

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    That's a pretty significant difference, which might also, in addition to rolling and axle friction and air drag, include an error in your recording of the velocity as it passed the light gate. The error tends to decrease as the angle increases, since the gravitational acceleratation becomes larger and starts to dwarf the frictional resistance. At small angles, the trolley might not even move if the axle friction is high. Such theoretical values of friction and air drag would be tough to calculate; I'd first check your velocity measurements. How much is the difference when say the angle is 45 degrees or more?
     
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