A 125-kg (including all the contents) rocket has an engine that produces a constant vertical force (the ?thrust?) of 1720 N. Inside this rocket, a 15.5-N electrical power supply rests on the floor. (a) Find the acceleration of the rocket. (b) When it has reached an altitude of 120 m, how hard does the floor push on the power supply? (?Hint:? Start with a free-body diagram for the power supply.)
Solution 12E a) The mass of the rocket is 125 kg. The thrust produced by the engine is 1720 N. So, the acceleration of the rocket is, 2 a = 1720 N / 125 kg = 13.76 m/s . b) The weight of the power supply when the rocket was at rest was 15.5 N. The mass of the power supply is, mass = 15.5 / 9.8 = 1.58 kg The normal reaction on the power supply by the floor of the rocket is, N = mg + ma = 15.5 N + 1.58 × 13.76 = 15.5 + 21.76 = 37.26. So, the floor pushes with 37.26 N force to the power supply. The free body diagram for the power supply is given below.
