Question

Water is flowing through a horizontal pipe with speed 2m/s and power required to maintain the flow is 20W. If speed becomes double , then power required will be ....?
1. 160W
2. 80W
3.320W
4. 40W

Answer 1

Water is flowing through a horizontal pipe with speed 2m/s and power required to maintain the flow is 20W. If speed becomes double , then power required will be 40W

Option 4 is correct

Power required ∝ Flow Rate  * Pressure

Velocity ∝ Flow Rate / Area

Power required ∝ Velocity ( as other factors are constant)

Power required = K Velocity

20 = k 2

=> k = 10

Power required = k (2 * 2)

=> power required = 10 * 4 = 40 W

Answer 2

answer : option (4) 40W

we know, Power = force applied × speed

given,

water is flowing through a horizontal pipe with speed 2m/s and power required to maintain the flow is 20W.

so, 20W = force applied × 2m/s

force applied = 10N........(1)

now question said, speed becomes double . e.g., speed = 4m/s

so, power = force applied × speed

from equation (1),

power = 10N × 4m/s = 40W

hence, power required will be 40W