Assume that the earth goes round the sun in a circular orbit with a constant speed of 30 kms
The average velocity of the earth from 1st jan, 90 to 30th June, 90 is zero.
The average acceleration during the above period is 60 km/s2.
The average speed from 1st Jan, 90 to 31st Dec, 90 is zero.
The instantaneous acceleration of the earth points towards the sun.
The instantaneous acceleration of the Earth points towards the Sun.
The speed is constant; therefore, there is no tangential acceleration and the direction of radial acceleration is towards the Sun. So, the instantaneous acceleration of the Earth points towards the Sun.