Advertisements
Advertisements
प्रश्न
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)
उत्तर
Work done in climbing or potential energy, (P.E) = 2500 J
Acceleration due to gravity, (g) = 10 m/s2
Height above the ground be, (h) = 5 m
Let the mass of the man be (m)
We have a relation as,
P.E = m × g × h
So, mass can be calculated as,
`m = (P.E)/(h xx g)`
so , mass of the man ,
`m = 2500/(5 xx 10)` kg
= `250/5` kg
= 50 kg
APPEARS IN
संबंधित प्रश्न
Define average power.
A battery lights a bulb. Describe the energy changes involved in the process.
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.
Calculate the work done by the brakes of a car of mass 1000 kg when its speed is reduced from 20 m/s to 10 m/s?
A body of mass 100 kg is lifted up by 10 m. Find :
(i) the amount of work done
(ii) potential energy of the body at that height (value of g = 10 m/s2)
A body does 1200 joules of work in 2 minutes. Calculate its power.
The power output of an engine is 3kW. How much work does the engine do in 20 s?
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
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)
Which one of the following statements about power stations is not true?
