Advertisements
Advertisements
Question
A man weighing 500 N carried a load of 100 N up a flight of stairs 4 m high in 5 seconds. What is the power?
Advertisements
Solution
Weight of the man, (W1) = 500 N
Weight of the load, (W2) = 100 N
Height, (h) = 4 m
Time taken, (t) = 5s
So total weight,
W = W1 + W2
= (500 + 100) N
= 600 N
We can calculate the work done against gravity as,Work done by the man is = (total weight)(vertical distance)
= (600)(4)
= 2400 J
Now, we can calculate the power of the man as,
Power = `"Work done"/"Time"`
So ,
Power = `2400/5` W
= 480 W
So , the power of man is 480 W .
APPEARS IN
RELATED QUESTIONS
Define 1 watt of power.
A battery lights a bulb. Describe the energy changes involved in the process.
What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.
What is the power of a body which is doing work at the rate of one joule per second?
An electric heater uses 600 kJ of electrical energy in 5 minutes. Calculate its power rating.
A car of weight 20000 N climbs up a hill at a steady speed of 8 m/s, gaining a height of 120 m is 100 s. Calculate : work done by the car.
A car of weight 20000 N climbs up a hill at a steady speed of 8 m/s, gaining a height of 120 m is 100 s. Calculate : power of engine of car.
Define power. Give the SI unit of power.
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
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)
