Suppose the earth revolves around the sun in a circular orbit, maintaining a constant speed of 30 km/s .

Step-by-step solution

In uniform circular motion, the instantaneous acceleration is the centripetal acceleration, which is always directed towards the centre of the circular path. Since the earth revolves around the sun in a circular orbit, its instantaneous acceleration is directed towards the sun. From 1st Jan to 30th June (approximately half a year), the earth completes half of its orbit. The displacement is equal to the diameter of the orbit, which is non-zero, making the average velocity non-zero. During this half-year period, the