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course phy 231
course phy 231Ball on V rampsUses ball, two ramps, dominoes, TIMER
See also Pictures_of_ball_and_ramps, which includes pictures and brief descriptions of basic setups.
Make the two ramps into a wide V, with each end supported by a single domino lying on its flat side. If the ball is released from the top of one ramp, it will roll down the the bottom of the V, then up the other ramp. If it doesn't roll off the end of that ramp, it will then return to the bottom of the V and roll back up the first ramp, but not as far as its original starting point. The ball will continue rolling back and forth until it comes to rest.
Release the ball from the top of the shorter ramp. Observe how far it travels from release to the bottom of the V, from the bottom of the V to its highest point on the other ramp, and how far it travels back up the first ramp before coming to beginning to roll back down.
Report your observations:
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To bottom of V from initial point is 5.9 inches
bottom of V to highest point on other ramp: 5.75 inches
Back up to highest point on small ramp: 3.1 inches
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Repeat, this time releasing the ball from the top of the longer ramp.
Report your observations:
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To bottom of V from initial point is 11.8 inches
To highest point on small ramp: 5.75 inches
Going back up to the highest on longest ramp: 5.25
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Using the TIMER, release the ball and observe the clock time of release, and the clock times when the ball reaches the bottom of the V, and the clock times when reaching the highest point of each ramp. Also observe the clock time at which the ball finally comes to rest.
Report the distances you observed in the first sets of trials.
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To highest point on long ramp, 5.3 inches; back up to short ramp, 3.1 on short ramp.
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Copy the TIMER output.
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0 at release, highest point on long ramp is 1.95 seconds. Highest point on short ramp time is 3.99 seconds. Time until rest is 13.3 seconds.
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Of each set of trials where you measured the distances, express each distance as a percent of the initial distance down the first ramp.
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First distance is 88 percent of initial “drop”; next distance is 51.7 percent of initial drop.
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According to your TIMER output does it take longer for the ball to go up the longer ramp, or down?
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I got the same time for each
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Analysis:
Assuming ball mass 60 grams and domino thickness .9 cm, how much gravitational PE did the ball lose between release and its first 'turnaround', and how much between that and its second 'turnaround'?
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Both the long and the short ramp have the same height since they are both resting on a single dominoe. The original PE when dropped from rest at the top of either ramp if F*displacement, so that is (.6kg)(9.81 m/s^2)(.009 m). so the original PE is .053 N, and the PE at the top of the other ramp is MG(.004 m){30/.9=14.6/x} where x is the height that corresponds to the distance up the ramp.
So the original PE is .0053 N and the PE of the “turnaround” is .0024 N, so the PE lost was .0053-.0024= .0029 N
PE is in Joules. This could cause confusion in subsequent calculations.
You used .6 kg; note that 60 grams is .060 kg.
Accepting the .6 kg for the moment, and .053 J would be correct.
The ramps are straight. You measure the positions of the 'turnaround' points. So you can figure out the gravitational PE at each 'turnaround' point.
You answer to the last question requires that you have first calculated the PE at each of these points. Having made those calculations, you will use this with additional information to answer that question.
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Assuming that the energy lost to rolling friction between two 'turnaround' points is proportional to the distance the ball rolls between those points, how much energy do you conclude was lost in the two 'bumps' at the bottom of the V?
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I think probably around half of the total lost PE because the way to ball rolled back and forth reminded me of a pendulum, and I know a pendulum doesn’t lose energy as fast as this V system did.
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"
Your analysis is good up to a point, but be careful of units and other details.
You haven't completed the analysis. See my notes.
&#Please see my notes and, unless my notes indicate that revision is optional, submit a copy of this document with revisions and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
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