An object of mass m is dropped from height h above a planet of mass m and radius r. find an expression for the object's speed as it hits the ground. express your answer in terms of the variables m, m, h, r and appropriate constants.

v = √(2 MGh) / R

Explanation:

Assuming that h is much smaller than R, we can say the acceleration of gravity is approximately constant during the fall.

Potential energy = Kinetic energy

mgh = 1/2 mv²

v = √(2gh)

v = √(2 (MG/R²) h)

v = √(2 MGh) / R

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

we don't care about the 150kg or the 2,500 meters. they don't make any difference.

read more on -

nah.   i'm just sleepy.