DP Physics (last assessment 2024)

Question 21M.2.HL.TZ1.a

Date	May 2021	Marks available	[Maximum mark: 2]	Reference code	21M.2.HL.TZ1.a
Level	HL	Paper	2	Time zone	TZ1
Command term	Explain	Question number	a	Adapted from	N/A

[Maximum mark: 2]

21M.2.HL.TZ1.a

A planet is in a circular orbit around a star. The speed of the planet is constant. The following data are given:

Mass of planet    $= 8.0 \times 10^{24}$ kg
Mass of star    $= 3.2 \times 10^{30}$ kg
Distance from the star to the planet R   $= 4.4 \times 10^{10}$ m.

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

[2]

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 ✓

Syllabus sections

Core

Core » Topic 6: Circular motion and gravitation » 6.1 – Circular motion

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

Core » Topic 6: Circular motion and gravitation

Question 21M.2.HL.TZ1.a

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