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Homework Help: Air hockey lab

  1. Oct 2, 2005 #1
    the lab involves an air hockey tab set up on a slight angle (one side is raised by a textbook) and the puck is pushed in such a way as to create what looks like a parabolic shape on the paper with carbon markings. The point is to determine if the motion is a projectile motion. So far, my group has calculating the velocity in the x- direction, but we're stumped as how to find acceleration in the y-direction, due to the fact that the table is on a slight slant. the force of friction is negilible against the puck and the table because of the force of air (hence the name air hockey). What i want is some idea of how to calculate the acceleratation due to gravity. a formula or steps would be nice... we can take it from there. thanks.
     
  2. jcsd
  3. Oct 2, 2005 #2
    Using the angle of the table, set up a free body diagram and look at how you can rearrange the vectors for Normal Force and Gravity to find the acceleration along the table.
     
  4. Oct 2, 2005 #3
    mmmhmmm.... thought so. but to find the angle of the table you would use the height of the table + book and the lenght, then the heigh from the table to the airtable top?
     
  5. Oct 3, 2005 #4

    andrevdh

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    Homework Helper

    From your explanation of the setup I gather that you have a recorded paper with markings of the puck position at constant time intervals.To prove that the y-acceleration of the puck was constant you need to draw a graph of the y-velocity of the graph as a function of time. If the gradient of such a graph is constant then you have proved that the acceleration is constant. This can be calculated from
    [tex]\overline{v_y}=\frac{\Delta y}{\Delta t}[/tex]
    The calculated y-velocities will be in the middle of the time intervals, since they are average values. If you do not have the time interval value you need to first draw the y-displacement vs time graph and then calculate the gradient of such graph in between the data points and use these gradients for the y-velocities.
     
  6. Oct 4, 2005 #5
    the time displacement between each track (recording of position of puck) is 30 ms....if that helps...
     
  7. Oct 5, 2005 #6

    andrevdh

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    To calculate the average y-velocity component of the puck for the second time interval:
    [tex]\overline {v_{y2}}=\frac{\Delta y2}{0.030}[/tex]
    This is the average y-velocity of the puck at a time in the middle of the interval. Also note that
    [tex]\Delta y[/tex]
    is positive in this case. When the puck is gowing down this quantity will be negative giving a negative y-velocity component!
     
    Last edited: Nov 29, 2006
  8. Oct 5, 2005 #7
    yup... figured that.
     
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