Date:
Name:
Partner:
2021.05.05
Butters Hu
Comparing the Speed of Objects with Different Shapes Rolling off the
Same Slope
1 Objective
Verify the speed of objects with different shapes rolling off the same slope through measuring the time (t)
those objects take to reach the bottom of the slope and the length (L) of the slope.
2 Theory
When an object rolls off a slope, its energy is conserved, if the friction is negligible. By using the
conservation of energy, the initial gravitational potential energy is equal to the final sum of both the
translational and rotational kinetic energy, which is given that GPE = KE r + KE T, so V theory = (2gh/(1+c))1/2
Vreal = x/t
3 Materials and Equipment
l
A long cuboid box
l
A wooden stick
l
An electronic scale
l
A graduated scale
l
A plastic bottle
l
A stopwatch
l
A foil ball
4 Procedure
Step 1: Use the graduated scale to measure the height of the top of the slope and the length of the slope,
record this height as h and the length of the slope.
Step 2: Use the electronic scale to measure each object, to ensure that each object has close amount of mass,
record the mass as m1, m2, m3.
Step 3: Places the water bottle on the top of the slope, and let it roll off the slope freely.
Step 4: Record the time that the water bottle reaches the bottom of the slope as T.
Step 5: Repeat Step 3 and Step 4 with the stick and the foil ball relatively.
5 Data
Table 1
h = 0.19 m L = 0.50 m
Object
Mass (g±0.1)
T1 (s)
T2 (s)
T3 (s)
wooden stick
13.4
0.90
0.80
0.75
13.3
1.06
0.98
1.10
13.3
0.92
0.88
0.96
empty plastic
bottle
foil ball
Table 2
Object
Average T
V real (m/s)
V theory (m/s)
stick
0.82
1.22
1.57
bottle
1.04
0.96
1.36
ball
0.92
1.08
1.63
Average T stick = (0.9s+0.8s+0.75s)/3 = 0.82 s
Average V real’ = L/T = 0.5m/0.82s = 0.61 m/s
V real = Average V real’ * 2 = 1.22
6 Analysis and Conclusions
1) This part, firstly you should compare the final average result with theoretical value (the true one) and
find the percent error. “Times new Roman”, “五号”
The percent error of stick = (1.57-1.22)/1.57*100% = 22.30%
The percent error of bottle = 29.41%
The percent error of ball = 33.74%
2) Then you can show and describe the findings you get from the sets of your data. For example, whether
all your data has the same deviation trend or not. Whether some group of data have special trend and
try to find the reason.
Theoretically, the speed of ball is the largest, the speed of bottle is the smallest. However, according to the
experiment results, the speed of stick is the largest, and the speed of bottle is the smallest. This error is
possibly caused by the reason that the hand-made foil ball is not round enough, so it separates from the
ground for a little bit sometimes. Also, the rough surface of the ball generates larger friction.
3) Finally, you can make a conclusion here based on all your analysis above.
The objects with the same mass, but different shapes, have different speeds. There are some unpredicted
factors in the experiments, so the results of experiment will possibly be different from the theory.