Question

An artificial planet is moving in a circular orbit of radius 42250 km. Calculate its speed in km/second if it takes 24 hours to revolve around the earth.

• A. $2.07\frac{km}{s}$
• B. $3.07\frac{km}{s}$
• C. $4.21\frac{km}{s}$
• D. $1.28\frac{km}{s}$

Answer 1

The correct option is (B) 3.07 km/s

Step 1, Given

The radius of the planet = 42250 km

Step 2, Finding the speed

Since the planet is moving in circular orbit its speed can be given as

Speed $=\frac{Circumferenceoftrajectory}{Timeperiod}$

Or, Speed $=\frac{2\pi R}{T}$

Putting all the values

$=\frac{2\times \pi \times 42250}{24\times 3600}$ $\frac{km}{s}$
$[\because 1hr=60\times 60=3600s]$

After solving

Speed = 3.07 km/s

Hence the speed of the planet in orbit is 3.07 km/s