Question

A motor boat moves at a steady speed of 8 m s-1 if the water resistance to the motion of the boat is 2000 N calculate the power of the engine

Answer 1

Newton #1 - If there is no NET force, momentum is constant. Here speed is steady (I assume in a straight course) and mass is constant so net force is zero.

Newton #2 - Action is equal and opposite to reaction. So Propulsion force forward must be equal and opposite to resistance.

Therefore - Propulsion force = 2000 N

Work = Force * distance
Power = work /second = force * distance/second

so
Power = 2000 N * 8 meters / second
= 16,000 Joules/second or Watts

This must be a Destroyer of something :)

Answer 2

physics - Damon, Tuesday, July 22, 2014 at 4:37am

Newton #1 - If there is no NET force, momentum is constant. Here speed is steady (I assume in a straight course) and mass is constant so net force is zero.

Newton #3 - Action is equal and opposite to reaction. So Propulsion force forward must be equal and opposite to resistance.

Therefore - Propulsion force = 2000 N

Work = Force * distance
Power = work /second = force * distance/second

so
Power = 2000 N * 8 meters / second
= 16,000 Joules/second or Watts

This must be a Destroyer of something :)

Answer 3

given speed =distance /time =8m/s
force = 2000N
power =work /time=force *displacement /time
=2000*8/1
=16000j/s