A motor is used to deliver water through a pipe. Let the motor have a power P initially. To double the rate of flow of water through the pipe, the power is increased to P’. What is the value of P’/P?
Answer & explanation
Correct answer: option 3
Power = Force x Velocity
= (Mass/Time) x Velocity2
= Rate of flow x Velocity2
Rate of flow = Area x Velocity
Doubling the rate of flow will double the velocity.
P = Rate of flow x Velocity2
P’ = (2 x Rate of flow) x (2 x Velocity)2
= 8P
P/P’ = 8.