Question

An overhead tank of capacity 10 k litre is kept at the top of building 15 m high. Water falls in tank with speed 5`sqrt2` m/s. Water level is at a depth 5 m below ground. The tank is to be filled in `1/2` hr. If efficiency of pump is 67.5% electric power used is ______ W.

पर्याय

• 843.75

• 843.76

• 743.75

• 643.75

Answer 1

An overhead tank of capacity 10 k litre is kept at the top of building 15 m high. Water falls in tank with speed 5`sqrt2` m/s. Water level is at a depth 5 m below ground. The tank is to be filled in `1/2` hr. If efficiency of pump is 67.5% electric power used is 843.75 W.

Explanation:

Work done by motor

= mgh + `1/2`mv² = 225 × 10000 J

Power of motor = `(225xx10000)/1800`W

∴ Electric power used

(P) = 67.5 % of power of motor

= `(67.5xx225xx10000)/((1800xx100)"W")`

= `(67.5xx225)/(18"W")`

= 843.75 W