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Question 18M.3.HL.TZ1.19a

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Date May 2018 Marks available [Maximum mark: 1] Reference code 18M.3.HL.TZ1.19a
Level HL Paper 3 Time zone TZ1
Command term Show that Question number a Adapted from N/A
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18M.3.HL.TZ1.19a

A galaxy can be modelled as a sphere of radius R0. The distance of a star from the centre of the galaxy is r.

M18/4/PHYSI/HP3/ENG/TZ1/19

For this model the graph is a simplified representation of the variation with r of the mass of visible matter enclosed inside r.

(a)

The mass of visible matter in the galaxy is M.

Show that for stars where r > R0 the velocity of orbit is v =  G M r .

[1]

Markscheme

m v 2 r = G M m r 2  and correct rearranging

[1 mark]

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