Advertisements
Advertisements
Question
In an experiment to measure his power, a student records the time taken by him in running up a flight of steps on a staircase. Use the following data to calculate the power of the student :
Number of steps = 28
Height of each step = 20 cm
Time taken = 5.4 s
Mass of student = 55 kg
Acceleration = 9.8 m s−2
due to gravity
Advertisements
Solution
Mass of the student, (m1) = 55 kg
Height of each step, (h) = 0.2 m
Number of steps, (n) = 28
So, total vertical height,
= (0.2) (28) m
= 5.6 m
Acceleration due to gravity, (g) = 9.8 m/s2
Time taken (t) = 5.4 s
We can calculate the work done against gravity as,
Work done by the car = (Weight of body) × (Vertical distance)
= (55) × (9.8) × (5.6) J
= 3018.4 J
Now, we can calculate the power of the boy as,
Power = `"Work done"/"Time"`
So ,
Power = `3018.4/5.4` W
= 558.96 W
= 559 W
So, the power is 559 W.
APPEARS IN
RELATED QUESTIONS
Define 1 watt of power.
What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.
A person holds a bundle of hay over his head for 30 minutes and gets tired. Has he done some work or not? Justify your answer.
Find the energy in joules consumed in 10 hours by four devices of power 500 W each.
How much is the mass of a man if he has to do 2500 joules of work in climbing a tree 5 m tall? (g = 10 m s−2)
Define kilowatt-hour.
A trolley is pushed along a road with a force of 400 N through a distance of 60 m in 1 minute. Calculate the power developed.
A boy weighing 40 kg carries a box weighing 20 kg to the top of a building 15 m high in 25 seconds. Calculate the power. (g = 10 m/s2)
Which one of the following statements about power stations is not true?
How is the power related to the speed at which a body can be lifted? How many kilograms will a man working at the power of 100 W, be able to lift at a constant speed of 1 m s–1 vertically? (g = 10 m s–2)
