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course phy 201
One lab activity:Conservation of Energy on a Ramp
Use an incline with a very small slope.
Strike the steel ball so it coasts up, comes to rest, then accelerates back down the incline. Let the ball continue to roll off the incline and fall to the floor, and mark the position at which it hits the floor. (Be sure you also mark the straight-drop position).
Also note the position on the incline at which the ball comes to rest before accelerating back down.
At the same time, using the TIMER program, record the time interval from the end of the 'strike' back to the end of the incline.
Repeat for at least two good trials.
Report your data:
Trial 1: 8.7cm up ramp, 2.23 seconds
Trial 2: 12.9cm up ramp, 2.64 seconds
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From each of the stopping points on the ramp, as you previously observed them, release the ball from rest and time it down the incline. Record the positions at which it strikes the floor.
Report your data:
Trial 1: 1.26 seconds, 9cm
Trial 2: 1.48 seconds, 8.25cm
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From your data, infer how long it took the ball to go up the ramp for each trial.
Calculate the ball's acceleration up the ramp, and its acceleration down the ramp.
Report your results, and indicate how they were obtained:
Trial 1: 0.97 seconds up ramp, 6.59cm/s2 up, 5.48cm/s2 down
Trial 2: 1.48 seconds up ramp, 7.73 cm/s2 up, 5.89cm/s2 down
For acceleration down of trial 1
Vf=8.7cm/1.26s
=6.90cm/s/1.26s
=5.48cm/s2
For the accelerations up I subtracted 2.5cm because I nudged the ball about 2.5cm from the end of the ramp.
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From your two accelerations, you can infer the coefficient of rolling friction. What is your result?
Average acceleration of both trials down/980cm/s2= 5.685cm/s2/980cm/s2= 0.0058
On our first trial the difference in the accelerations up and down is about 1 cm/s^2.
For the second trial the difference is about 2 cm/s^2.
The difference between the two accelerations is the result of the difference between frictional force up, and frictional force down. The magnitude of this difference is double the frictional force. So the frictional force itself would result in an acceleration between 1/2 cm/s^2 and 1 cm/s^2.
The conclusion is that mu for rolling friction is between .0005 and .001.
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The large ball has diameter 2.5 cm, the small ball diameter 2.0 cm. The ball is made of steel with an approximate density of 8 grams / cm^2.
Find the KE the ball attained while rolling down the ramp with the PE it lost while rolling down. Compare the two:
Volume=4/3(pi)r3
Volume= 4.19cm3
8g/cm2=m/4.19cm3
m=33.5g
KE=.5(33.5g)(6.9cm/s)^2
KE=79.7 joules
Very good. However see my notes about the coefficient of friction.
You should still do the PE calculation.
Check out Class Notes.
&#Good responses. Let me know if you have questions. &#
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