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# University Physics

1. Look up the mean radius of the Sun and its mean distance from Earth. From these data, calculate the angular size of the Sun.

2. Suppose the directions of rotation and revolution of a planet are the same, and a year of the planet consists of 10 planet's sidereal days. What is the duration of the planet's solar day in terms of its sidereal day? Why?

3.Rotational axis of the Earth precesses, but the revolution axis is fixed. (a) Does ecliptic, defined as the apparent path of the Sun relative to other stars, move? (b) Does the vernal equinox move?

### 1 Answer

- 天同Lv 79 years agoFavorite Answer
1. Radius of the sun = 6.96 x 10^8 m

Sun-earth distance = 1.5 x 10^11 m

Hence, diameter of the sun = 2 x 6.96x10^8 m

Angular size of the sun = 2 x 6.96x10^8/1.5x10^11 radians = 0.00928 radians

2. Since there are 10 sideral days in one year, there will then be 9 solar days.

Hence, duration of one solar day = 10/9 sideral day = 1.11 sideral day

3. (a) No.

(b) Yes.

Please refer to the following web-page for explanation: