A satellite mass 80kg is in orbit around the earth at a distance 7.5R where R is the mean radius of the earth. If the gravitational field is 9.8N/kg at the earth surface and R = 6400km. a)Centripetal force acting on the satellite b) The period of the satellite of the orbit in hours.

Here's the solution to your problem:

We are given the following information:

• Mass of the satellite, $m = 80 \text{ kg}$
• Orbital radius from the center of the Earth, $r = 7.5R$, where $R$ is the mean radius of the Earth.
• Gravitational field strength at the Earth's surface, $g_0 = 9.8 \text{ N/kg}$
• Mean radius of the Earth, $R = 6400 \text{ km}$

First, let's convert $R$ and $r$ to meters:
$R = 6400 \text{ km} = 6400 \times 10^3 \text{ m} = 6.4 \times 10^6 \text{ m}$
$r = 7.5R = 7.5 \times 6.4 \times 10^6 \text{ m} = 48 \times 10^6 \text{ m} = 4.8 \times 10^7 \text{ m}$

The gravitational field strength at the Earth's surface is $g_0 = \frac{GM_E}{R^2}$, where $G$ is the gravitational constant and $M_E$ is the mass of the Earth. From this, we can express $GM_E = g_0 R^2$.