Download Circular Motion Lab

LAB REPORT
CIRCULAR MOTION
Procedure:
1. Measure the mass of the hook and the mass of the rubber stopper (constant) and record it.
2. Cut a piece of string, approximately 75 cm long, and tie one end to the rubber stopper, put the
end through the glass tube, and then tie it to the hook.
3. Measure 30 cm from the stopper and use the white-out to paint a white strip on the string and
record this as the radius of the circle.
4. Place a weight on the hook and attempt to spin the rubber stopper in a circle. Make sure the
white mark on the string stays very close to the edge of the glass to keep the radius fixed.
5. When you have mastered this, have a partner time 10 complete cycles and record this. You
should be able to calculate the period from this. Complete 3 trials.
6. Repeat steps 4 and 5 but with additional weights on the hook until you have sufficient data.
Raw and Processed Data:
S. NO
LENGTH OF
STRING
WEIGHT OF RUBBER
CORK
WEIGHT OR SUSTAINED
MASS
TIME
AVERAGE
Weight one – Trial 1
30
22.7
32.74
4.31
4.73
Weight one – Trial 2
30
22.7
32.74
4.94
Weight one – Trial 3
30
22.7
32.74
4.94
Weight two – Trial 1
30
22.7
52.74
4.41
Weight two – Trial 2
30
22.7
52.74
4.81
Weight two – Trial 3
30
22.7
52.74
4.79
Weight three – Trial
1
30
22.7
72.74
4.63
Weight three – Trial
2
30
22.7
72.74
5.10
Weight three – Trial
3
30
22.7
72.74
4.82
Weight four– Trial 1
30
22.7
92.74
4.63
Weight four– Trial 2
30
22.7
92.74
4.85
Weight four– Trial 3
30
22.7
92.74
4.78
Weight five - Trial 1
30
22.7
112.74
4.90
Weight five - Trial 2
30
22.7
112.74
4.09
Weight five - Trial 3
30
22.7
112.74
4.19
4.67
4.85
4.75
4.39
Calculations:
Trial 1:
((4*pi*pi*0.3)/9.81) * 22.7 * (1/ (0.473^2)) = 122.49421 ~ 122.5
Error discrepancy = (Experimental – theoretical) / theoretical *100
=> (122.5-32.74) / 32.74 *100 = 274.14 %
Trial 2:
((4*pi*pi*0.3)/9.81) * 22.7 * (1/ (0.467^2)) = 125.662033 ~ 125.7
Error discrepancy = (Experimental – theoretical) / theoretical *100
=> (125.7-52.74) / 52.74 *100 = 138.33 %
Trial 3:
((4*pi*pi*0.3)/9.81) * 22.7 * (1/ (0.485^2)) = 116.507629 ~ 116.5
Error discrepancy = (Experimental – theoretical) / theoretical *100
=> n(116.5-72.74) / 72.74 *100 = 60.16%
Trial 4:
((4*pi*pi*0.3)/9.81) * 22.7 * (1/ (0.475^2)) = 121.464851~ 121.46
Error discrepancy = (Experimental – theoretical) / theoretical *100
=> (121.46-92.74) / 92.74 *100 = 30.97%
Trial 5:
((4*pi*pi*0.3)/9.81) * 22.7 * (1/ (0.439^2)) = 142.203014 ~ 142.20
Error discrepancy = (Experimental – theoretical) / theoretical *100
=> (142.0-112.74) / 112.74 *100 = 25.95 %
Error Analysis:
1) Systematic errors:




The velocity of the string was not steady.
 If the velocity of the string was not steady, then the time-period would get
affected because the faster the velocity is, the more the time-period will be and
the slower the velocity is, the lower the time-period will be. This directly
impacts our results in finding the experimental weight of the mass sustained as
the time-period of the object could be farther away from its true value.
The radius was not kept constant due to varying velocity.
 If the radius was not kept constant throughout the experiment, the value for v
(from formula v = rω) would be different at different points in time. Since the
velocity is affected, the value for the time-period may also change which affects
our error discrepancy rate as well.
The stopwatch was not used properly.
 The misuse of the stopwatch could, again, lead to an error in the time-period,
making it greater or lesser than its true value, which impacts our calculations.
This in turn, affects our error discrepancy as depending on the time -period we
may get a larger or smaller value of the sustained mass.
The measurement for the radius of the string used was not taken correctly.
 If the measure of the radius was not taken correctly, it directly implies that
there is going to be a huge difference in the obtained value for the sustained
mass and its true value. This is because in the formula, radius is a factor, that if
changed can drastically impact the results of the experiment.
2) Random errors:



Delay in stopping stopwatch.
 Due to human instinct, there could have been a delay in stopping the
stopwatch, leading to an increase or decrease in the time-period which
indirectly affects the value for our experimental value.
Delay in starting stopwatch.
 Due to human instinct, there could have been a delay in starting the stopwatch,
leading to an increase or decrease in the time-period which indirectly affects the
value for our experimental value.
Level at which the rubber mass was rotated.
 If the level at which the rubber mass was rotated, changed at any point in time,
the amount of resistance offered by the glass tube would vary which could
directly affect the time taken for the rubber mass to complete ten rotations.
This indirectly affects the experimental value of the sustained mass.