# The orbital period of the satellite is 90 minutes, the satellite’s height above the earth is 320 km

**The orbital period of the satellite is 90 minutes, the satellite’s height above the earth is 320 km, the radius of the earth is 6.400 km. Find the satellite speed?**

To find the orbital speed of the satellite, we write the formula for the speed of a body’s revolution around a circle:

u = 2πr / T,

where r is the distance from a point on the circle to its center (radius);

T is the period of revolution of the body along the circumference.

We see that in this problem the radius will be the sum of the earth’s radius and the satellite’s height:

r = R + h.

We substitute it in the formula for the speed of rotation of the body:

u = 2π (R + h) / T = (2 * 3.14 * (6400 km + 320 km)) / 1.5 h = 6.28 * 6 720 km / 1.5 h = 42201.6 / 1 .5 = 28 134.4 km / h.

Answer: 28,134.4 km / h.