Page 88 - text book form physics kssm 2020

Th e eff ects of mass and distance between two objects on File
gravitational force are shown in Figure 3.7.
Even though gravitational force
F F 1
1 is a universal force, two persons
on the Earth’s surface will not
F F feel the effect of the gravitational
2 2
force. This is because the
gravitational force between two
The larger the mass of the body, Gravitational force decreases when the bodies of small mass has a very
the larger the gravitational force. distance between the two bodies increases. small magnitude. For example,
F F F F two persons of masses 50 kg
1 2 1 2
and 70 kg respectively, only
Figure 3.7 Eff ects of mass and distance between two bodies on gravitational force experience a gravitational force
–7
Gravitational force between two bodies depends on the of 2.3 × 10 N if they stand at a
mass of the bodies, as well as the distance between them. distance of 1 m from each other.

Activity 3.3 Abstraction CPS

Aim: To solve problems involving Newton’s Universal Law of Gravitation for
(i) objects on the Earth’s surface
(ii) the Earth and satellite
(iii) the Earth and the Sun
Instructions:
1. Work in pairs.
2. Study Figure 3.8 and answer the questions.

The Sun The Moon
Mass = 1.99 × 10 kg Mass = 7.35 × 10 kg
22
30
Distance between the Earth
11
and the Sun = 1.50 × 10 m The Earth
Mass = 5.97 × 10 kg
24
Radius = 6.37 × 10 m
6
Man-made satellite
Mass = 1.20 × 10 kg
3
Distance between the Earth
and the satellite = 4.22 × 10 m
7
Figure 3.8 Th e Sun, the Earth, the Moon and a man-made satellite
Discussion:
1. What is the gravitational force on the man-made satellite before it is launched?
2. Compare:
(a) the mass of the Earth, the mass of the man-made satellite and the mass of the Sun
(b) between the Earth-satellite distance and the Sun-Earth distance.
3. Predict the difference in the magnitude of the gravitational force between the Earth and
the man-made satellite and the gravitational force between the Sun and the Earth.
4. Calculate:
(a) the gravitational force between the Earth and the man-made satellite
(b) the gravitational force between the Earth and the Sun.
Does your answer match your prediction in question 3?
20
5. The gravitational force between the Earth and the Moon is 2.00 × 10 N. What is the
distance between the centre of the Earth and the centre of the Moon?

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3.1.2