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Physics Form 4 Chapter 2 Force and Motion I

ACTIVITY 2.2

Aim: To determine the value of gravitational
acceleration Diameter = d cm Steel ball
Apparatus and Materials: Photogate A
Photogate kit and electronic timer, steel ball, Time passing through
micrometer screw gauge photogate A = t s
1
Instructions:
1. The arrangement of the apparatus is
shown in Figure 2.39.
2. A pair of photogates is arranged at
different heights.
3. A steel ball is dropped and falls through Time passing through = t s Photogate B
Chapter
2 both the photogates, each equipped with photogate B 2
optical sensors that can measure the
time, t, of an object falling through it.
4. The diameter of the steel ball, d, is
measured with a micrometer screw
gauge.
Results:
Electronic timer
Diameter of the steel ball = d cm Figure 2.39
Time for the steel ball to pass through
photogate A = t 1 s
Time for the steel ball to pass through photogate B = t 2 s
Time for the steel ball to travel from photogate A to photogate B = t s
Calculations:
d
Average velocity of steel ball in passing photogate A, u = cm s .
–1
t 1
d
Average velocity of steel ball to passing photogate B, v = cm s .
–1
t 2
Time taken for the steel ball to accelerate from u to v = t s
v – u
Using the formula a = , the experimental value of gravitational acceleration is,
t
d – d
v – u
g = = t 2 t 1 cm s –2
t t
–2
This value can be divided by 100 to convert to m s for easier comparison with standard value.
Discussion:
The scientific estimation for the value of g at the equator is around 9.78 m s and at the poles is
–2
about 9.83 m s .
–2
Usually, the experimental value is lower than the scientific value because of the existence of air
resistance as the steel ball falls.

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