power. numericals 9th cbse

Power numericals

1. A machine does 192 J of work in 24 Sec. What is the power of the machine?

2.A weighting 50kg runs up a hill rising himself vertically 10m in 20Sec. Calculate power. given g = 9.8m-2

3.A weighting 50kg runs up a hill rising himself vertically 10m in 20Sec. Calculate power. given g = 9.8m-2

4.A athlete weighing 60kg runs up a staircase having 10 steps each of 1m in 30 sec. Calculate power (g = 9.8ms-2

5.The heart does 1.5 J of work in each ) heartbeat. How many times per minute does it beat if its power is 2watt?

6.
Calculate the time taken 60 w bulb to consume 3000 J of energy . (50sec.

7.horse cart system moves with velocity 36kmh-1 on the level road., then find the power of horse in term of horse power (1hp=746W) 

8 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 due to gravity = 9.8 m s−2

9.The power of a heart which beats 72 times in a minute is 1.2kW. Calculate the work done by heart for each beat. ( 1kJ)

10 Whenn loading a truck, a man lifts boxes of 100 N each through a height of 1.5 m.

(a) How much work does he do in lifting one box ?

(b) How much energy is transferred when one box is lifted ?

(c) If the man lifts 4 boxes per minute, at what power is he working ? (g = 10 m s−2)

11.Define 1 watt of power.

12.lamp consumes 1000 J of electrical energy in 10 s. What is its power ?

13.An electric heater is rated 1500 W. How much energy does it use in 10 hours?

14.A boy of mass 40 kg runs up flight of 50 steps each 10 cm high in 5 seconds. Find: (i) the work done by the boy. (ii) the power developed, (g = 9.8 ms-2)

15.Calculate the power of an engine required to lift 10s kg of coal per hour from a mine 360 m deep, (Take g = 10ms-2).

16.A woman pulls a bucket of water of total mass 5 kg from a well which is 10 m in 10 s. Calculate the power used by her. [Take g = 10 ms-2]

17.a) Define average power.
(b) A lamp consumes 1000 J of electrical energy in 10 s. What is its power?
(c) Give the commercial unit of energy in Joules. [SAll-2013]

18.motor boat moves at a steady speed of 4 ms – 1. Water-resistance acting on it is 4000 N. Calculate the power of its engine. (16kW)

19.A man pulls a block with a force of 300 N through 50 m in 60 s. Find the power used by him to pull the block.

20.A 50 kg man moved 25 steps up in 20 seconds. Find his power, if each step is 16 cm high. (100 W)

21.Calculate the power of a pump which can lift 200 kg of water through a height of 6 m in 10 seconds. (1200 watts)

22.How is the power related to the speed at which a body can be lifted? How many kilogrims will a man working at the power of 100 W, be able to lift at constant speed of 1 mr1 vertically? (g = 10 ms

23.A car of mass 2000 kg is lifted up a distance of 30 m by a crane in 1 minute. A second crane does the same job in 2 minutes. What is the power applied by each crane?

24 Avinash can run with a speed of 8 m/s against the frictional force of 10 N, and Kapil can move with a speed of 3 m/s against the frictional force of 25 N. Who is more powerful and why?

25.What is power? How do you differentiate kilowatt from kilowatt-hour? The Jog falls in Karnataka state are nearly 20 m high. 2000 tonnes of water falls from it in a minute. Calculate the equivalent power if all this energy can be utilized. (g = 10 ms-2)

26 A rickshaw puller pulls the rickshaw by applying a force of 100 N. If the rickaw moves with constant velocity of 36 kmh-1. Find the power of rickshaw puller. (1000w)

27.A athlete weighing 60kg runs up a staircase having 10 steps each of 1m in 30 sec. Calculate power (g = 9.8ms-1 ) (ans: 200W)

28.Calculate the time taken 60 w bulb to consume 3000 J of energy . (50sec. )

29.The power of a heart which beats 72 times in a minute is 1.2kW. Calculate the work done by heart for each beat. ( 1kJ)

30.