A 500kg Moon lander has a velocity of 10 m/s downward when it is a certain height above the ground. 1 minute later, it is 1 m from the ground and its speed is 0.5 m/s downward. Assume that the thruster on the lander fires upward with a constant force. Moon's gravitational field strength near its surface is 1.6 N/kg.
 What is the force by the exhaust on the lander (i.e. thrust)?
 What was its initial height, when its speed was 5 m/s downward?
