The document compares the work done by three pumps to fill water tanks from a well. Pump A fills its 1000L tank in 100 seconds, Pump B takes 200 seconds, and Pump C takes 400 seconds. Although each pump lifts 1000kg of water 15m, the amount of work done per second (power) differs between pumps due to their varying fill times, with Pump A having the highest power of 1500J/s and Pump C the lowest at 375J/s. Power is calculated by dividing work done by time taken, and is measured in watts (J/s).

2. Working of pumps in three neighbouring houses
PUMP VOLUME OF
WATER
MASS OF
WATER
HEIGHT FROM
THE WATER
LEVEL IN
WELL(h)
TIME TAKEN
FOR THE
TANK TO BE
FILLED
WORK
W = mgh
A 1000L 1000 kg 15 m 100 s 150000 J
B 1000L 1000 kg 15 m 200 s 150000 J
C 1000L 1000 kg 15 m 400 s 150000 J

3.  What is the amount of work done by the pump A to fill water in the tank?
What is the work done by the pump B?
 What is the work done by the pump C?
 Is the amount of work done by the pump to fill water in the three tanks same?

4. W = mgh = 1000 x 10 x 15 m = 1000 kg
= 150000 J g = 10 m/s
h = 15 m

5. Let’s find the amount of work done per second by each pump
PUMP
WORK DONE
(J)
TIME
(s)
WORK DONE BY
SECOND J/S
A 150000 J 100 s 1500 J/s
B 150000 J 200 s 750 J/s
C 150000 J 400 s 375 J/s

6. POWER
Work done per unit time or rate of doing work is power
Power = Work/ time , 𝑝 =
𝑤
𝑡
Unit of power = Unit of work/ Unit of time = J/s
joule per second is called watt (W)
1kW = 1000W
1 HP = 746W

7. A Horse Power or 1 HP is the power of a
horse. This is estimated as about 746 W.

8. LET’S DO PROBLEM
 If a man of mass 70 kg climbs up a mountain of
height 30 m in 5 minute, what is his power?