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
A lamp consumes 1000 J of electrical energy in 10 s. What is its power?
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.
Define kilowatt-hour.
Fill in the blank with suitable word :
Power is the rate of doing ___________.
Fill in the blanks with suitable words :
One watt is a rate of working of one ___________ per ___________.
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?
The power output of an engine is 3kW. How much work does the engine do in 20 s?
Define power. Give the SI unit of power.
An electric motor raises a load of 0.2 kg, at a constant speed, through a vertical distance of 3.0 m in 2 s. If the acceleration of free fall is 10 m/s2, the power in W developed by the motor in raising the load is :
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)
