1. The problem statement, all variables and given/known data The space shuttle Endeavor is moving at a speed of 27870 Km / h. At takeoff, its mass is 2, 28 * 10 ^ 6 kg, however, its mass decreases as it uses its fuel: the engine burns liquid oxygen which has a density of 1141 kg / m^3, at a rate of 1340 liters per second. Calculate the rate of change of the gravitational force exerted by earth on the shuttle, at the time the rocket is 20 km in height. 2. Relevant equations 3. The attempt at a solution I know I have to derivate the formula but I don't get any relation where I can get the dm/dt that results after derivating. Thanks for help. So sorry for my English.