Question

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 $1$st Jan, $90$ to $30$th June, $90$ is zero
• B. The average acceleration during the above period is $60km/s^2$
• C. The average speed from $1$st Jan, $90$ to $31$st Dec, $90$ is zero
• D. The instantaneous acceleration of the earth points towards the sun

Answer 1

Answer: (D)

The instantaneous acceleration of the earth points towards the sun

The average velocity of the earth from $1$st Jan, $90$ to $30$th June, $90$ is $\frac{totaldisplacement}{totaltime}$

Since in this period, displacement is finite, the average velocity is also finite.

The average speed from $1$st Jan, $90$ to $31$st Dec, $90$ is equal to the the instantaneous speed, since speed is constant. During this period, average velocity is zero.

Instantaneous acceleration of the earth points towards the Sun and is equal to $\frac{m{v}^2}{r}$(centripetal acceleration).