Assume that the earth goes round the sun in a circular orbit with a constant speed of 30km/s. (a) The average velocity of the earth from 1st Jan, 90 to 30th June, 90 is zero. (b) The average acceleration during the above period is 60kn/s2. (c) The average speed from 1st Jan, 90 to 31st Dec, 90 is zero. (d) The instantaneous acceleration of the earth points towards the sun.
