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
A lamp consumes 1000 J of electrical energy in 10 s. What is its power?
Define kilowatt-hour.
Name the physical quantity whose unit is watt.
Fill in the blanks with suitable words :
One watt is a rate of working of one ___________ per ___________.
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.
The power output of an engine is 3kW. How much work does the engine do in 20 s?
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.
Define power. Give the SI unit of power.
In loading a truck, a man lifts boxes of 100 N each through a height of 1.5 m.
If the man lifts 4 boxes per minute, at what power is he working?
(g = 10 m s−2)
