Solutions to Exercise 1

1. The time period is 2 hours = 7200 seconds. The diameter is thus

D = ( 100 km/s ) x 7200 s = 7.2 x 105 km

The radius is 1/2 of this (3.6 x 105 km), and since the solar radius is 6.96 x 105 km, this is 0.52 solar radii.
2. The time period is 7 hours = 25,200 seconds. Proceeding as above,

D = ( 100 km/s ) x 25,200 s = 2.52 x 106 km

The radius is 1/2 of this (1.26 x 106 km), which is 1.8 solar radii.