Question

Spaceman Spiff is flying his rocket on patrol when he gets a distress call. Space pirates are attacking a freighter near the Moon. The freighter’s shields will hold for another ten minutes, then they will be out of power. Spiff needs to be traveling at 400 km/s to reach the freighter before the shields fail. If he goes slower, he won’t get there in time, and if he is going faster, he won’t be able to stop without flying past the freighter. Spiff is cruising at 10 km/s when he gets the call. If his rocket has a mass of 35,000 kg, how much work will the engines on Spiff’s rocket have to do for him to rescue the freighter?

Answer 1

I think here we need to use Impulse - momentum relation.

Impulse = Change in momentum

Force * time = mass (final velocity - initial velocity)

Force * 10 * 60 = 35000 (400,000 m/s - 10,000 m/s)

Force * 10 * 60 = 35000 (390000)

Force = 2.275e7 N

In this question, it is not clear whether the work or force is required because usually engine apply force on the vehicle. Anyway, I have done the main calculation. You just need to find the out whether force or work is required.

Please let me know if you have any doubt or you come up with some new information.