Advertisements
Advertisements
Question
How long should an electric motor, of power 2 H.P. operate, so as to pump 5 m3 of water from a depth of 15m. [Take g = 10 N kg−1]
Solution
Mass of water = v × d = 5m3 × 1000 kg m−3 = 5000 kg.
Height = 15 m, t = ?, g = 10 N kg−1
P = 2 H.P. = 2 × 750 = 1500 W
Work done in operating electric motor = P × t = 1500 W × t
Work done in raising water = mgh = 5000 × 10 × 15 = 750000 J
1500 × t = 750000 J
t = 500 seconds.
APPEARS IN
RELATED QUESTIONS
An object thrown at a certain angle to the ground moves in a curved path and falls back to the ground. The initial and the final points of the path of the object lie on the same horizontal line. What is the work done by the force of gravity on the object?
What is the work done by the moon when it revolves around the earth?
What are the two kinds of mechanical energy?
A man lifts a mass of 20 kg to a height of 2.5 m. Assuming that the force of gravity on 1 kg mass is 10 N, find the work done by the man.
A weight lifter lifted a load of 200 kgf to a height of 2.5 m in 5 s. Calculate:
- the work done, and
- the power developed by him. Take g = 10 N kg-1
How much work is done when a body of mass m is raised to a height h above the ground?
Fill in the blank with suitable word :
The work done on a body moving in a circular path is __________
Choose one or more correct alternatives.
For work to be performed, energy must be ______.
- transferred from one place to another
- concentrated
- transformed from one type to another
- destroyed
When you move upstairs, do you perform some work?
A man carrying a suitcase in his hand is walking horizontally. What is the work done against gravity?
A cricket ball is thrown up from the earth's surface. What happens to its P.E.
(a) during the motion
(b) at the highest point?
How much energy is gained by a box of mass 20 kg when a man, runs carrying the box with a speed of 3 m/s-1 to catch the bus?
Name the material commonly used for the manufacturing of solar cells.
(i) A 200g ball is thrown vertically upward with an initial velocity of 30 ms-1. Draw a velocity-time graph for the motion of ball.
(ii) How long will the ball take to reach the highest point?
(iii) What will be the kinetic energy of ball, when it returns to the starting point, neglecting the air resistance?
(iv) What will be the potential energy of ball at highest point?
The weights of two bodies are 2.0 N and 2.0 kgf respectively what is the mass of each body?
