Form 4-5 Acc – G

Theme 1:
On the Move
Aim: Experiment to investigate the acceleration due to
gravity .
OBJECTIVE: To study uniformly accelerated linear motion and to
determine the acceleration due to gravity, g.
Focus Questions
When Galileo dropped two different sized spheres from the tower of
Pisa, which one touched earth first? The large or small sphere? Why?
If Galileo dropped a hammer and a feather from the tower which one
will fall first?
And if this experiment is done on the moon will there be a
difference? Why?
What force is pulling the objects towards earth?
Do objects falling freely have the same acceleration provided there
are no opposing forces?
Do you know the value for this acceleration?
Does the velocity of a free-falling object increases with time?
When measuring the distance h between light gates be careful to avoid parallax
error .Make sure that the ball is released as close to the first light gate as possible
so that initial velocity is nearly zero. Make sure that the light gates are horizontal
and vertically aligned. The ball must be dropped directly above the first light gate.
Measurements should be repeated as much as possible. The diameter of plasticene
should be measured as accurately as possible.
Ninu Cremona Lyceum – Gozo College – Physics Department
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Date: ____________
Theme 1:
On the Move
Aim: Experiment to investigate the acceleration due to gravity.
Apparatus: Retort stand and clamp, Nova 5000 data logger, plasticene balls,
ruler, two light gates, a table tennis ball.
Sources of error and precautions 
1. Press the plasticene into a round ball. Adjust each light gates on a clamp and
stand. Switch Nova 5000 on. Ensure that the AC/DC adapter is connected.
2. Attach the first light gate to Input 1 (I/O-1) of the Nova5000 and the second
light gate to Input 2 (I/O-2) of the data logger. Launch MultiLab software.
Click Tools on the menu bar, and then click Unit Settings and click Select
Plot, Choose Input : Voltage – choose 3 decimal places. Repeat for
input 2.
3. Click Logger on the menu bar, and then click Timing Wizard. Choose Time
and click timing wizard – Method. Choose between gates. Press OK.
4. Adjust the light gates so that the distance between them is around 20 cm. One
student holds the plasticene directly above the light gate. Release the
plasticene ball and record the time taken using the data logger. This is
repeated four times so that an average could be calculated.
5. Increase the distance between the light gates by around 10cm and record the
results. Repeat four more times. All data is recorded in table 1.
6. Predict what would happen if a tennis ball of same shape is used. Which is the
heavier? Would the gravity be the same or will it increase? Now test your
prediction by finding the acceleration using Data logger.
7. Click Logger on the menu bar, and then click Setup. Choose Rate and choose
100 samples per second. Click Samples and choose 500. Press OK. Press
Run. Drop the plasticene ball . Wait for the logger to stop.
Ninu Cremona Lyceum – Gozo College – Physics Department
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8. To find Acceleration -- Press Tools – Analysis – Timing analysis –
Acceleration - Timing wizard – Method –Between gates - Enter width
of ball in cm. Press Ok. Record Acceleration. Press run and repeat with
table tennis ball.
Table 1
fallen - m
Time -1
Time - 2
Time - 3
Time - 4
Time - s
Table 2
Time s
V = s / t
The acceleration due to gravity in m/s2 was found using the equation –
s = ut + ½ g t2
since we are assuming that initial velocity u is zero then we can write
g = 2 s / t2
Using table 2 plot a graph of 2s against t2. Use the graph to
find g
Ninu Cremona Lyceum – Gozo College – Physics Department
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Acceleration of table tennis ball- __________________ m/s
Acceleration of plascticene ball- __________________ m/s
Acceleration of plasticene ball - __________________ m/s
obtained from graph
1. Draw a diagram of the experiment apparatus?
2. Calculate the gradient of the graph. What should the slope or
gradient of the graph be equal to?
3. What do you notice about the values of velocity as the heights
fallen are increased?
4. Small variations between individual results should be observed
and possible sources of error discussed. For example how precise
was the height measurement, was the fall wobble-free, was the
initial velocity of the dropped plasticene zero?
5. Comment on what your graphs say. Did you obtain a straight
line? If not why? Does it start from zero? Why?
6. Will a large values of height fallen give more accurate values of
g. Why?
7. Does the free fall acceleration depends on the body’s weight ? On
using a tennis ball was the time taken different or was it the
same? Is the value of g affected by the size of the ball?
8. Explain how it is that all bodies fall with the same acceleration?
Ninu Cremona Lyceum – Gozo College – Physics Department
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