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Date May 2021 Marks available 2 Reference code 21M.2.SL.TZ1.2
Level Standard level Paper Paper 2 Time zone 1
Command term Determine Question number 2 Adapted from N/A

Question

A planet is in a circular orbit around a star. The speed of the planet is constant.

Explain why a centripetal force is needed for the planet to be in a circular orbit.

[2]
a.i.

State the nature of this centripetal force.

[1]
a.ii.

Determine the gravitational field of the planet.

The following data are given:

Mass of planet            =8.0×1024 kg
Radius of the planet    =9.1×106 m.

[2]
b.

Markscheme

«circular motion» involves a changing velocity

«Tangential velocity» is «always» perpendicular to centripetal force/acceleration

there must be a force/acceleration towards centre/star

without a centripetal force the planet will move in a straight line

a.i.

gravitational force/force of gravity ✓

a.ii.

use of GMR2 ✓

6.4 «Nkg−1 or ms−2» ✓

b.

Examiners report

[N/A]
a.i.
[N/A]
a.ii.
[N/A]
b.

Syllabus sections

Core » Topic 6: Circular motion and gravitation » 6.2 – Newton’s law of gravitation
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Core » Topic 6: Circular motion and gravitation
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