This document provides instructions for a science worksheet on work, power, and energy. It contains 50 multiple choice and short answer questions across several sections. The questions cover topics like calculating work, power, energy, kinetic energy, potential energy, conservation of energy, and their relationships and applications. Students are asked to calculate values, define terms, provide reasoning and explanations, and solve conceptual problems involving these physics concepts. The document specifies that all questions are compulsory and marks are provided for each question.

1. @MOHIT SIR-9891389128,9958991220
1 / 4
Maximum Marks: 150 Time Allowed: 3 hours
SKM TUTORIALS
T-1,G-01 GULMOHAR GARDHAN RAJ NAGAR EXTENTION GZB
Class 09 - Science
Worksheet on Work,Power and Energy
General Instructions:
All questions are Compulsory
.
Marks are given in front of each question.
Section A
a) b) 3600
c) d)
1. 60 W means that the device will use 60 joule of energy in ______ hour. 1
1
360
1
60
1
3600
a) He does 200 joules of work per metre b) He does zero work against force of
gravity
c) The work done against gravity is equal to
the muscular energy
d) The work done against gravity cannot be
estimated but non-zero
2. A man holds and displaces a 20 kg mass horizontally in his stretched hand. 1
a) different pressure in both cases b) greater pressure in case of student A
c) greater pressure in case of student B d) same pressure in both cases
3. To observe and compare the pressure, student A takes the solid iron cuboid while B takes its alloy. Both of
them measure the weight of cuboids with the help of a spring balance and find them equal. If both of the
students perform the experiment with the face having the same dimensions then they will observe
1
a) E = Pt b)
c) d)
4. One unit of electricity is consumed by A : P = 40 W bulb used for t = 25 hours
B : P = 20 W bulb used for t = 50 hours
Both A and B are true as, energy E in kWh is best related as
1
E =
t
1000
E =
pt
1000
E =
p
100
a) energy b) power
c) component d) displaces
5. Work done is said to be positive if the applied force has a _____ in the direction of displacement. 1
a) 10 m b) 245,000 m
c) 960 m d) 98 m
6. A total of 4900 J was spent in lifting a mass of 50 kg. the mass was raised to a height of 1
a) joule b) kilowatt hour
c) kilowatt d) newton metre
7. Which one of the following is not the unit of energy? 1
a) direction b) power
c) position d) energy
8. The potential energy of a body is by virtue of its ______________ 1
a) person is sitting in a chair b) person is sitting on the ground
c) person is lying on the ground d) person is standing
9. Potential energy of a person is minimum when: 1

2. @MOHIT SIR-9891389128,9958991220
2 / 4
Section B
a) 245 J b) 25 J
c) 50 J d) 2.5 kJ
10. An object of mass 5 kg falls from a height of 5 m above the ground. The loss of potential energy of the mass
is
1
11. Why a dead body floats, with its head immersed in water. 3
12. Write an expression for the kinetic energy of an object. 3
13. A mass of 10 kg falls from a height of 50 cm. Calculate (i) Velocity of the body (ii) Kinetic energy of body
when it just reaches the ground level. Does the velocity depend upon the mass of the particle? Explain.
(Take g = 10 ms-2)
3
14. A man rowing a boat upstream is at rest with respect to the shore. Is he doing work? 3
15. A solid weighs 100 gf in air and 88 gf when completely immersed in water. Calculate : i) the upthrust (ii)
the volume of the solid and (iii) the relative density of the solid.
3
16. Calculate the work done in lifting 200 kg of a mass through a vertical distance of 6 m. Assume g = 10 m/s2. 3
17. A battery lights a bulb. Describe the energy changes involved in the process? 3
18. A certain household has consumed 250 units of energy during a month. How much energy is this in joule? 3
19. Calculate the work done against the gravity. 3
20. A man whose mass is 50 kg climbs up 30 steps of a staircase, each measuring 20 cm high, in 30 s. Calculate
the power used in climbing the stairs. (Take g = 10 ms-2)
3
21. A man of mass 60 kg runs up a flight of 30 steps in 15 seconds. If each step is 20 cm high, calculate the
power developed by the man. (Take g = 10 m/s).
3
22. In each of the following a force, F is acting on an object of mass, m. The direction of displacement is from
west to east shown by the longer arrow. Observe the diagrams carefully and state whether the work done
by the force is negative, positive or zero.
3
23. Justify giving proper reasoning whether the work done in the following cases is positive or negative
a) Work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket
b) Work done by gravitational force in the above case.
3
24. An engine can pump 30,000 litres of water a vertical height of 45 metres in 10 minutes. Calculate the work
done by the machine and its power. [g = 9.8 m/s2; Density of water = 103kg/m3, 1000 litre = 1 m3].
3
25. Why an egg sinks in fresh water but floats in a strong solution of salt? 3
26. A test tube loaded with lead shots weighs 50 gf and floats upto the mark 'X' in water. The test tube is then
made to float alcohol. It is found that 10 gf of lead shots have to be removed, so as to float it to level 'X'.
Find RD of alcohol.
3
27. Which would have greater effect on kinetic energy of an object - doubling the mass, or doubling the
velocity?
3
28. What is the relationship between the commercial unit and SI unit of energy? 3
29. Calculate the work required to be done to stop a car of 1500 kg moving at a velocity of 60 kmh-1. 3
30. A machine raises a load of 750 N through a height of 16 m in 5 seconds. Calculate the power at which the
machine works.
3
31. Give reason : Ice bergs floating in the sea are dangerous for the ship. 3
32. Define average power. 3
33. A force of 20 N displaces a body through a distance of 1 m at an angle of 60° from its own direction.
Calculate the amount of work done.
3
34. A body moves along a circular path. How much work is done in doing so? Explain. 3
35. A girl having a mass of 35 kg sits on a trolley of mass 5 kg. The trolley is given an initial velocity of 4 ms-1
by applying a force. The trolley comes to rest after traversing a distance of 16 m.
a. How much work is done on the trolley?
b. How much work is done by the girl?
3
36. Why does a block of plastic released under water come up to the surface of water? 3

3. @MOHIT SIR-9891389128,9958991220
3 / 4
Section C
37. If an electric iron of 1200 W is used for 30 minutes every day, find the electric energy consumed in the
month of April.
3
38. If an electric bulb of 100 watt is lighted for 2 hours. how much electric energy would be consumed? 3
39. The Jog falls in Karnataka state are nearly 20 m high 2,000 tonnes of water falls from it in a minute.
Calculate the equivalent power, if all this energy can be utilised. (g = 10 ms-2)
3
40. How are kinetic energy and momentum related? 3
41. Derive an expression for the kinetic energy of the body? Calculate the kinetic energy for a body of mass 5
Kg moving a velocity 2.5 m/s2
.
5
42. Show that total energy is conserved if the ball of mass 'm' is the thrown downwards from a height 'h'. 5
43. Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a
pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? What
happens to its energy eventually? Is it a violation of the law of conservation of energy?
5
44. The area of cross-section of the stem of a hydrometer is 0.32 cm2 and its length is 20 cm. Its mass is 22.8 g
and volume of the bulb is 10 cm3.
Find.
i) The density of the liquid in which it floats upto its midpoint.
ii) The density of the liquid in which it is completely immersed.
5
45. a. Give one example of each of the following:
i. Small mass but high kinetic energy
ii. Large mass but low kinetic energy
b. Prove mathematically that the total mechanical energy of a freely falling body in air is conserved.
5
46. The volume of a 500 g sealed tin is 350 cm-3. What is the density of the packed tin? Will the packet float or
sink in water if it has a density 1 g cm-3? What will be the mass of water displaced by this tin? What will be
the relative density of the packed tin?
5
47. A car of mass 900 kg is travelling at a steady speed of 30 m/s against a resistive force of 2000 N, as
illustrated in figure.
i. Calculate the kinetic energy of the car.
ii. Calculate the energy used in 1.0 s against the resistive force.
iii. What is the minimum power what the car engine has to deliver to the wheels?
iv. What form of energy is in the fuel, used by the engine to drive the car?
5
48. Figure shows a conveyor belt transporting a package to a raised platform. The belt is driven by a motor.
i. State three types of energy, other than gravitational potential energy, into which the electrical energy
supplied to the motor is converted.
ii. The mass of the package is 36 kg. Calculate the increase in the gravitational potential energy (p.e.) of
the package when it is raised through a vertical height of 2.4 m.
iii. The package is raised through the vertical height of 2.4 m in 4.4 s. Calculate the power needed to raise
the package.
iv. Assume that the power available to raise package is constant. A package of mass greater than 36 kg is
raised through the same height. Suggest explain the effect of this increase in mass on the operation of
the belt.
5
49. Look at the activities listed below. Reason out whether or not work is done in the light of your
understanding of the term ‘work’.
5

4. @MOHIT SIR-9891389128,9958991220
4 / 4
(a) Suma is swimming in a pond.
(b) A donkey is carrying a load on its back.
(c) A wind-mill is lifting water from a well.
(d) A green plant is carrying out photosynthesis.
(e) An engine is pulling a train.
(f) Food grains are getting dried in the sun.
(g) A sailboat is moving due to wind energy.
50. A man standing on the top of a tower 60 m high throws a ball in the vertically upward direction with a
velocity of 20 ms-1. How long will it take the ball to pass by the man while moving in the downward
direction? How long will it take the ball to hit the ground? (Take g = 10 ms-2)
5