Download Chapter # 7 Work Power and Energy PDF

TitleChapter # 7 Work Power and Energy
TagsPower (Physics) Potential Energy Kinetic Energy Mass
File Size151.3 KB
Total Pages13
Document Text Contents
Page 1

PHYSICS CHAPTER # 07
Work, Power & Energy

1. Work is said to be done when a body is moved or stopped through certain distance by the action of:
a) Energy b) Force
c) Power d) Momentum

B

2. When work is done _______ is transferred to the body or taken out of the body:
a) Energy b) Force
c) Power d) Momentum

A

3. During The process of doing work energy is transferred to the body or taken out of the body in the form
of:

a) Kinetic energy b) Potential energy
c) Momentum d) Force

A

4. Work is a product of:
a) Power and time b) Energy and displacement
c) Force and energy d) Force and distance

D

5. The magnitude of work done by a force f through a distance d acting at angle  is given by:
a) fd sin  b) fd tan 

c) fd cos  d) d
f

cos 

C

6. In the vector form, the work done is:

a) f


 d


b) d


 f


c) 2

1

f


 d


d) f


. d


D

7. Work done is maximum when force is _______ to displacement:
a) Equal b) Perpendicular
c) Opposite d) Parallel

D

8. For certain values of F and d, work done is zero when the angle between the force and displacement is:
a) 0o b) 30o

c) 90o d) 180o

C

9. The magnitude of work is maximum in the opposite direction when the angle  is equal to:
a) 0o b) 45o

c) 90o d) 180o

D

10. The units of work are the same as those of:
a) Power b) Energy
c) Force d) Mass

B

11. The force acting on a body in the gravitational field at any point is equal to its:
a) Gravitational mass b) Weight
c) Acceleration d) Inertia

B

12. The work done in a gravitational field is independent of:
a) Its distance b) Its mass
c) Its path d) Its potential energy

C

13. A field is said to be conservative if the work done along a closed path is:
a) Zero b) Negative
c) Positive d) Infinity

A

14. The rate of doing work is called:
a) Energy b) Power
c) Force d) Inertia

B

15. Power is defined as:

a) Work Time

Work

d) Work  distance

C

16. The SI unit of power is:
a) Joule b) Erg
c) Dyne d) Watt

D

17. In the vector form power is expressed as:

a) P = F


. V


b) P = F


 V


c) P = V


 F


d) P = F


. d


A

18. One kilowatt-hour is a unit of:
a) Power b) Energy
c) Time d) Velocity

B

19. One kilowatt-hour is equal to _______ joules:
a) 3.6  109 b) 6.3  109
c) 3.9  106 d) 3.6  106

D

Bahadur Ali Qureshi - 1 -

Page 2

PHYSICS CHAPTER # 07
Work, Power & Energy

20. The formula for the kinetic energy is given by:

a) K.E = m2V2 b) K.E = 2

1

mV2

c) K.E = mV d) K.E = 2

1

m2V

B

21. The potential energy of a body of mass m placed at height of h is:

a) 2

1

mg2 b) 2

1

mgh
c) mgh d) 2 mgh

C

22. The work done in lifting a body to a higher level is stored in it as:
a) Power b) Moment of inertia
c) Kinetic energy d) Potential energy

D

23. One horse-power is equal to _______ watts:
a) 647 b) 446
c) 746 d) 646

C

24. Ability to do work is called:
a) Power b) Energy
c) Torque d) Force

B

25. The potential energy of a bodyis defined as the energy it possesses due to its _______:
a) Mass b) Weight
c) Velocity d) Position

D

26. According to the work-energy principle work done on body is equal to:
a) The difference of its final and initial momentum
b) The difference of its final and initial potential energies
c) The difference of its final and initial kinetic energies
d) The difference of its velocities

C

27. The work done in moving a body from the surface of the earth to a point at infinite distance is called
its:

a) Kinetic energy b) Absolute work
c) Absolute potential energy d) None of the above

C

28. The absolute potential energy of a body of mass m at the surface of the earth is given by:

a)
2

e

e

R

GmM

b) e

e

R

GmM

c)
3

e

e

R

GmM

d) ee
MR

Gmg

B

29. The escape velocity at the surface of the earth can be found by the formula:

a) V = e
gR2

b) V = e
gR

c) V = 2

1
egR d) V = 2g e

R

A

30. The value of the escape velocity on the surface of the earth is:
a) 1100 m sec-1 b) 11 m sec-1

c) 11000 m sec-1 d) 11  106 m sec-1

C

31. If a body falls from a height, the relation between its kinetic and potential energies is:
a) Gain in K.E = Loss in P.E - Work done against friction
b) Gain in P.E = Loss in K.E + Work done against friction
c) Loss in K.E = Gain in P.E + Work done against friction
d) Loss in P.E = Gain in K.E - Work done against friction

A

32. When a falling body hits the earth, its kinetic energy changes to:
a) Potential energy b) Chemical energy
c) Sound & heat d) Mechanical energy

C

33. The ultimate source of almost all the energy that we use is:
a) Water b) Air
c) The sun d) Petroleum

C

34. Geothermal energy is produced:
a) When sun rays strike the earth b) In the interior of the earth
c) When ocean waves strike the rocks d) Due to earth’s magnetism

B

35. The tidal energy is produced due to rotation of the earth relative to:
a) Moon b) Sun
c) Oceans d) Water

A

Bahadur Ali Qureshi - 2 -

Page 6

PHYSICS CHAPTER # 07
Work, Power & Energy

92. The kinetic energy of a body depends upon:
a) Force and acceleration of the body b) Density and weight of the body
c) Mass and velocity of the body d) Mass and density of the body

C

93. Which quantity is not a scalar quantity?
a) Work b) Power
c) Kinetic energy d) Torque

D

94. The kinetic energy of a 100 gm bullet moving at a speed of 100 m/s is:
a) 2500 J b) 500 J
c) 1250 J d) 250 J

B

96. The energy of a meteorite as it enters into earth’s atmosphere, is converted into:
a) Kinetic energy b) Mechanical energy
c) Heat energy d) Nuclear energy

C

98. Watt is the unit of power, kilowatt-hour is the unit of:
a) Power b) Work
c) Momentum d) Energy

D

99. Wind blows from areas of:
a) High pressure to areas of low pressure b) Low pressure to areas of high pressure
c) Low temperature to areas of high temperature d) None of these

A

100. Which of the following is the biggest unit of energy?
a) joule b) Watt-hour
c) Kilo watt-hour d) Erg

C

102. When two protons are brought closer:
a) The P.E. between them decreases b) The P.E. between them increases
c) The P.E. between them remains unchanged d) Their K.E. increases

B

105. To increase the span of the jump, a long jumper should jump:
a) At an angle of 90o b) At an angle of 60o

c) At an angle of 45o d) As high as possible

C

106. When the mass and speed of a body are doubled, its kinetic energy becomes:
a) 2 times b) 4 times
c) 6 times d) 8 times

D

107. A gas filled balloon possesses:
a) Kinetic energy b) Potential energy
c) Both kinetic and potential energy d) None of these

B

108. A stone tide to the end of a 10 cm string is whirled in a horizontal circle. If centripetal acceleration is
10 m/s2, its linear speed in m/s is:
a) 10 b) 1
c) 100 d) 0.1

B

109. What is the P.E. lost by a stone of mass 10 Kg when it is dropped from a 10 m high building:
a) Zero b) 98 joules
c) 100 joules d) 980 joules

D

110. Which of the following is not a fundamental unit?
a) Candela b) Area
c) Kelvin d) Ampere

B

111. Which of the following quantities is dimensionless?
a) Volume b) Momentum
c) Angle d) Density

C

113. Angular momentum of a body about a fixed point is conserved if its velocity is:
a) Constant b) Variable
c) Directly proportional d) None of these

A

114. The escape velocity of a body depends on:
a) Mass of the body b) Mass of the planet
c) Density of the planet d) None of these

B

115. When a torque acting on a system is zero, which of the following will be constant?
a) Linear momentum b) Angular momentum
c) Impulse d) Force

B

116. A paratrooper of mass 80 kg descends vertically at a constant velocity of 3 m/s. Taking the
acceleration of free fall as 10 m/s2, what is the net force acting on him:
a) 800 N b) Zero
c) 240 N d) 360 N

B

117. A mass is projected vertically upwards with a given velocity. Neglecting air resistance, which one of
the following statements is correct?
a) The momentum of the mass ins conserved throughout the motion
b) The total energy of the mass is conserved throughout the motion
c) The Kinetic energy of the mass is maximum at the maximum height
d) The potential energy increases uniformly with time

B

Bahadur Ali Qureshi - 6 -

Page 7

PHYSICS CHAPTER # 07
Work, Power & Energy

118. A positron of mass 10-30 Kg (a light particle) is moving with a speed V. It makes a head-on elastic collision
with a stationary proton of mass 10-27 Kg (a heavy particle). Which one of the following correctly describes the
outcome of the collision?

a) The positron comes to rest and the proton moves on with speed V
b) The positron rebounds with speed V and the proton moves on with speed V
c) The positron rebounds with speed V and the proton moves on at a speed very much less than V

(almost at rest)
d) The positron rebounds at speed V/2 and the proton moves on at speed V/2

C

119. A car of mass m has an engine which can deliver power P. What is the minimum time in which the
car can be accelerated from rest to a speed v?

a) P

mv

b) mv

P

c) P2

mv2

d)
2mv

P2

C

121. A body of mass 10 Kg is moving at a speed of 5 ms-1. Its kinetic energy is:
a) 50 j b) 0.125 j
c) 250 j d) 125 j

D

122. A man pulls a trolley through a distance of 50 m by applying a force of 100 N which makes an angle
of 30o with the horizontal. Work done by the man is:
a) 2500 j b) 4330 j
c) 5000 j d) 1.732 j

B

123. The work performed on an object does not depend upon:
a) Force applied b) Angle at which force is inclined to the

displacement
c) Initial velocity of the object d) Displacement

C

124. Work done by a centripetal force is _______ because centripetal force is always at right angle to the
direction in which the body is moving:
a) Negative b) Positive
c) Zero d) None of these

C

125. The work done will be negative if angle between force F and displacement d is:
a) 60o b) 90o
c) 180o d) 360o

C

126. The rate of doing one joule of work in one second is called:
a) One kilowatt hour b) One horse power
c) One - watt d) None of these

C

127. 1 Joule = _______ ergs:
a) 103 b) 105

c) 107 d) 108

A

128. “The work done by the applied force is equal to the change in kinetic energy” This is known as:
a) Work energy principle b) Law of conservation of energy
c) Law of conservation of angular momentum d) None of these

A

129. Work – Energy equation is represented by:
a) Loss of P.E. = Gain in K.E.
b) Loss of P.E. = Gain in K.E. + work done against friction
c) Loss of P.E. = Gain in K.E. - work done against friction

d) Loss of P.E. =
frictionagainstdoneWork

.E.KinGain

B

130. When the force is parallel to the direction of motion of the body, then work done on the body is:
a) Infinity b) Zero
c) Maximum d) Minimum

C

131. When a body is lifted through a height “h” the work done on the body appears in the form of:
a) Force b) Work
c) Potential energy d) Momentum

C

132. Power can be expressed in units:
a) Kilowatt hour b) Ergs per seconds
c) Horse power hour d) None of these

B

134. If the mass of an object is doubled then its kinetic energy becomes _______ times:
a) Half b) Two
c) Three d) Four

B

135. The formula of kinetic energy is:

a)
2

2

v

m2

b) m2

v2

c) 2mv2 d) ½ mv2

D

Bahadur Ali Qureshi - 7 -

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