Question

B2. A tank on the roof of a 20 m high build- ing can hold 10 m3 of water. The tank is to be filled from a pond on the ground in 20 minutes. If the pump has an effi- ciency of 60 %, then the input power in kW is 1) 1.1 2) 2.74 3) 5.48 4) 7.0 3 An electric f 3​

Answer 1

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>>A tank on the roof of a 20 m high buildi

Question



A tank on the roof of a 20 m high building can hold 10m3 of water. The tank is to be filled from a pond on the ground in 20 minutes. If the pump has an efficiency of 60%, the input power required is

A

1.1kW

B

2.72kW

C

5.48kW

D

7.0kW

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Solution



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Correct option is B)

1 m3 of water is 1000 L and weigh 1000 kg. 

So, the weight of 10 m3 is 10000 kg. 

So, mass m=10000 kg

Height, h=20 m

Gravitational acceleration, g=9.8 m/s2

Time, t=20×60 sec 

Since efficiency of the pump is 60%, we can write that,

10060P=tmgh

P=60×20×6010000×9.8×20×100=2.72 kW