Question

A 1400-kg rocket has a net propulsion force of 80 kN (kiloNewtons). Over a short time period, it uniformly speeds up from an initial velocity of 30 m/s to a final velocity of 55 m/s. Assume that the mass of the rocket is constant during this time period and that the net force is along the direction of motion. What is the net work done on the rocket in kilojoules (kJ)?

Answer 1

14875 kilojoules

Step-by-step explanation:

m = Mass of rocket = 1400 kg

F = Force of the propulsion = 80 kN

u = Initial velocity of the rocket = 30 m/s

v = Final velocity of the rocket = 55 m/s

Work done by the rocket is given by the kinetic energy

`K=(1)/(2)m(v^2-u^2)\\\Rightarrow K=(1)/(2)1400(55^2-30^2)\\\Rightarrow K=1487500\ J`

The net work done on the rocket is 1487500 Joules or 14875 kilojoules