College Physics 2.5 – The Earth’s Average Speed & Velocity

(a) Calculate Earth’s average speed relative to the Sun.

(b) What is its average velocity over a period of one year?


Part A

The average speed of the earth is equal to the distance traveled divided by the time.

\displaystyle \text{Average speed of the Earth}=\frac{\text{Distance Traveled}}{\text{Total time of Travel}}=\frac{2\pi \text{r}}{\text{t}}

\displaystyle =\frac{2\pi \left(1.50\times 10^{11}\text{ m}\right)}{365.25\:\text{days}}\times \frac{1\:\text{day}}{24\:\text{hours}}\times \frac{1\:\text{hour}}{3600\:\text{sec}}

\displaystyle =2.99\times 10^4\:\text{m/s}

Part B

After a period of 1 year, the planet Earth has already returned to its original position with respect to the Sun. This means that we do not have any displacement. Therefore, the average velocity is zero.

\displaystyle \text{Average velocity}=0\:\text{m/s}