Page 90 - text book form physics kssm 2020

Activity 3.5 Logical Reasoning CPS

Aim: To discuss the variation in the values of g with r Gravitational acceleration
Instructions: below the surface of the Earth
1. Work in pairs.
2. Calculate the value of gravitational acceleration for the
fi ve distances given in Figure 3.10.

• Mass of the Earth, M Earth http://bt.sasbadi.com/p4084
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= 5.97 × 10 kg
• Radius of the Earth, R
6
= 6.37 × 10 m R 2R 3R 4R 5R
• Gravitational constant, G
2
= 6.67 × 10 –11 N m kg –2

3. Complete Table 3.2. Figure 3.10

Table 3.2
R 2R 3R 4R 5R
Distance from centre of the Earth, r
Gravitational acceleration, g / m s –2

Discussion:
1. What is the value of gravitational acceleration on the Earth’s surface?
2. Plot a graph of g against r.
3. How does the value of gravitational acceleration change when the distance from the
centre of the Earth increases?
4. Discuss the condition where the value of gravitational acceleration is almost zero.

Figure 3.11 shows a sketch of a graph with various values of gravitational acceleration, g
and distance, r from the centre of the Earth.

g

GM
g = –––
R 2 Value g is inversely
proportional to the square
Value g is directly of the distance from centre
proportional to the distance of the Earth for r R.
from the centre of the Earth
for r R.

0 r
R 2R 3R

Figure 3.11 Variation of g with r
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84 3.1.3
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3.1.3