Find the speed with which the moon orbits the Earth. (The Earth-Moon distance is 3 . 8 × 10 8 m . Take the mass of the Earth to be 5 . 97 × 10 24 kg and G = 6 . 67 × 10 - 11 N m 2 kg - 2 )

To revolve the Moon a centripetal force is needed Which is provided by the gravitational force between the Moon and the Earth. F C e n t r i p e t a l = F G r a v i t a t i o n a l M m v 2 r = G M m M E r 2 v = G M E r Here, r is the distance between the Moon and the Earth. V = 6 . 67 × 10 - 11 × 5 . 97 × 10 24 3 . 8 × 10 8 = 1 . 02 × 10 3 m s - 1

The diagram shows equipotential surfaces due to two spherical masses. Using the diagram, explain how it can be deduced that masses are unequal.

In this diagram we can see that the pattern is not symmetrical. It implies that masses are not the same, the distortion in the spherical equipotential surfaces of the two masses is different.

MEDIUM

Diploma

IMPORTANT

Earn 100

What is the gravitational potential energy stored in the gravitational field between the Earth and the Moon $?$

Important Questions on Fields (HL)

MEDIUM

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 10 - Fields (HL)>Test yourself>Q 3

What is the Earth's gravitational potential at the position of the Moon

?

HARD

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 10 - Fields (HL)>Test yourself>Q 3

Find the speed with which the moon orbits the Earth. (The Earth-Moon distance is

3.8 \times 10^{8} m

. Take the mass of the Earth to be

5.97 \times 10^{24} kg

and

G = 6.67 \times 10^{- 11} N m^{2} {kg}^{- 2}

)

HARD

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 10 - Fields (HL)>Test yourself>Q 4

A spacecraft of mass

30000 kg

leaves the Earth on its way to the Moon and lands on the Moon. Plot the spacecraft's potential energy as a function of its distance from the Earth's centre. (The Earth-Moon distance is

3.8 \times 10^{8} m

. Take the mass of the Earth to be

5.97 \times 10^{24} kg

and the mass of the Moon to be

7.35 \times 10^{22} kg

HARD

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 10 - Fields (HL)>Test yourself>Q 5

The diagram shows the variation with distance from the centre of the planet of the gravitational potential due to the planet and its Moon. The planet's centre is at $r = 0$ and the centre of the Moon is at $r = 1$ . The units of separation are arbitrary. At the point where $r = 0.75$ the gravitational field is zero.

Question Image

Determine the ratio of the mass of the planet to that of the Moon.

HARD

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 10 - Fields (HL)>Test yourself>Q 5

Question Image

With what speed must a probe be launched from the surface of the planet in order to arrive on the surface of the Moon $?$

MEDIUM

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 10 - Fields (HL)>Test yourself>Q 6

The diagram shows a planet orbiting the Sun counter-clockwise, at two positions- $A$ and $B$ . Also shown is the gravitational force acting on the planet at each position. By decomposing the force into components normal and tangential to the path (dotted lines), explain why it is only the tangential component that does work. Hence, explain why the planet will accelerate from $A$ to $P$ but will slow down from $P$ to $B$ .

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