**Question 5: **The gravitational force acting on a satellite is always directed towards the center of the earth. Does this force exert torque on the satellite?

Answer

The gravitational force acting on the satellite is given by

F= (GM_{e}m)/r^{2} ————- (A)

Where M_{e} is mass of the earth.

m is mass of the satellite.

r is the distance of the satellite from the earth.

G is the gravitational constant = 6.67 x 10^{-11} N m^{2}/kg^{2}

This force provides the centripetal force keeping the satellite in its orbit. The torque is given by the equation.

Now the force applied on the satellite given in equation (A) is directed to the center of the earth. Such forces are called central forces. Both r and F have the same line of action and the the sine value is zero. Therefore, this force produces no torque.

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