Question

An artificial planet is moving in a circular orbit of radius $42250km$. Calculate its speed if it takes $24\text{hours}$ to revolve around the earth.

• A. 2.07 km/s
• B. 3.07 km/s
• C. 4.21 km/s
• D. 1.28 km/s

Answer 1

The correct option is B

3.07 km/s

Speed is defined as the ratio of the total distance travelled to the time taken $\left(T\right)$.

Distance, $s=2\pi R$​
where $R$ is the orbital radius.​​​​​​

Speed:
$v=\frac{2\pi R}{T}$
$v=\frac{2\times \pi \times 42250}{24\times 3600}$
$[\because 1hr=60\times 60=3600s]$
$⟹v=3.07km{s}^{-1}$