Question

A satellite is moving in a circular orbit around the earth due to gravitational force. What is the effect on gravitational force and speed if the radius of orbit is reduced?

• A. Gravitational force decreases and speed decreases
• B. Gravitational Force decreases and speed increases
• C. Gravitational Force and speed remains the same
• D. Gravitational Force increases and speed decreases
• E. Gravitational Force increases and speed increases

Answer 1

The correct option is E Gravitational Force increases and speed increases

The gravitational force $F=\frac{GMm}{r^2}$

If radius of orbit is reduced , the value of r will decrease. Thus, the gravitational force will increase.

Due to circular motion the centripetal force is equal to gravitational force i.e,

$\frac{m{v}^2}{r}=F$

From this, as F increases so velocity also increases.