A-level Physics (Advancing Physics)/Large Units/Worked Solutions

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1. What is one parsec in m?

206265 AU x 150 x 109 = 3.09 x 1016m

2. Convert 3 light days into km.

c = 3 x 105kms-1

3 x 3 x 105 x 24 x 60 x 60 = 7.78 x 1010km

3. Convert 5.5 parsecs into light years.

1 ly = 9.46 x 1015m

5.5 pc = 5.5 x 3.09 x 1016m = 1.70 x 1017m

Divide by 1 ly in metres to get a final answer of approximately 18ly.

4. The difference in angle of a star on the perpendicular to the plane of the Earth's orbit which passes through the Sun when viewed from either side of the Earth's orbit is 0.1°. How far away is the star in parsecs?

The angle between the perpendicular and the line which goes through the Earth is 0.05° = 180". So, the star is 1/180 pc away.