A communication satellite of mass 500 kg revolves around the earth in a circular orbit of radius $4.0 \times {10}^7 \mathrm{m}$ in the equatorial plane of the earth in the direction from west to east. The magnitude of angular momentum of the satellite is

As the satellite is revolving around earth in equatorial plane with orbital radius $4 \times {10}^7 \mathrm{m}$

Hence, the satellite is geostationary satellite.

The time period. T = 24 h = 86400 s

Velocity of satellite, v = $\frac{2\mathrm{\pi r}}{\mathrm{T}}$

Angular momentum, L = mvr

$\mathrm{L} = \mathrm{m}\left(\frac{2\mathrm{\pi r}}{\mathrm{T}}\right)\mathrm{r} = \frac{2\mathrm{\pi m}}{\mathrm{T}}{\mathrm{r}}^2$

L = $\frac{2\times 3.14\times 500}{86400}\times {(4\times {10}^7)}^2$

= 0.58 $\times {10}^{14} \mathrm{kg} {\mathrm{m}}^2{\mathrm{s}}^{-1} (\mathrm{approx}.)$