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PHYSICS > UNIT#02 WORK AND ENERGY > Flashcards

UNIT#02 WORK AND ENERGY Flashcards

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1
Q

A truck and a car move with equal velocity. On applying brakes, both will stop after a certain distance.

A

The car will cover less distance before stopping

being lighter than a truck, the car has less kinetic energy

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2
Q

What sort of energy does a flying bird possess?

A

➡Potential Energy

➡Kinetic Energy

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3
Q

When the velocity of an aeroplane is doubled, the momentum ____.

A

Is conserved

as the momentum of air also increases

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4
Q

A machine gun fires 60 bullets per minute, with a velocity of 700m/s. If each bullet has a mass of 50g, find the power developed by the gun

A

12250W

P=W/t=K.E/t

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5
Q

A bullet fired from a gun can pierce a target due to its

A

Kinetic Energy

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6
Q

Kinetic energy with any reference must be:

A

Positive

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7
Q

At what angle, work done will be maximum?

A

0°

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8
Q

Which one of the following is a greater work?

A

-1000J

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9
Q

Work done will be zero if the angle between Force and Displacement is;

A

270°

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10
Q

A force 2i + j has moved its point of application from (2,3) to (6,5). What is work done?

A

+10
(➡d=(6-2)i + (5-3)j
➡W=Fd)

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11
Q

At what angle the work done will be half of its maximum value:

A

60°

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12
Q

A man pushes a wall with 50N and it displaces it zero m, his work done is:

A

No work

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13
Q

If a mass of 5kg is lifted up to 5m height, what will be the work done against the gravitational field

A

245J

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14
Q

A person walks 2m with an acceleration of 5 m/s2, holding an object of mass 2kg. The net work done on the object is:

A

20J

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15
Q

A force of 3i+2j+4k N gives a displacement of 10jm. The work done is:

A

20J

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16
Q

A body travels displacement of 10m by force of 5N. If work done is 25J then the angle between F and d is:

A

60°

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17
Q

A person holds a bucket of wight 60N. He walks 7m along the horizontal path and climbs up a vertical distance of 5m. The work done by the gravity is:

A

300 N-m

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18
Q

Suppose the force and displacement of a particle in the direction of force are doubled. Work would be:

A

4 times

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19
Q

A person is holding a bucket by applying a force of 10N. He moves a horizontal distance of 5m and then climbs a vertical distance of 10m. Could you find the total work done by him?

A

100J

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20
Q

A gardener pushes a lawn roller through a distance of 20m. If he applies a force of 20kg weight in a direction inclined at 60° to the ground, find the work done by him

A

1960J

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21
Q

If velocity is double, then:

A

Momentum increases 2 times and K.E increases 4 times

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22
Q

What will be the ratio of an alpha particle and proton kinetic energies if their linear momentum is the same?

A

1:4

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23
Q

The bodies of one kg and four kg have the same kinetic energy. The ration in their momenta will be:

A

1:2

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24
Q

The velocity and momentum of a moving body are 10000 cm/s and 10000 g cm /s respectively. The K.E will be:

A

Four Times

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25
Q

The momentum and kinetic energy of a ball are numerically equal. The numerical velocity is;

A

2 m/s

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26
Q

The kinetic energy of a body moving at the speed of 10m/s is 30J. If its speed becomes 30m/s, its K.E will be:

A

270J

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27
Q

Car X is travelling at half the speed of ar Y. Car X has twice the mass of car Y. Which statement is correct?

A

Car X has half the kinetic energy of car Y

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28
Q

A ball of mass 2kg and another of mass 4kg are dropped together from a 60 feet tall building. After a gall of 30 feet each towards earth, their respective kinetic energies will be in the ratio of:

A

1:2

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29
Q

A bomb of mass of 30kg at rest explodes into two pieces of masses 18kg and 12kg. The velocity o 18kg mass is 6 m/s.The K.E of other masses is:

A

486J

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30
Q

The kinetic energy acquired by a body of mass m is travelling some distance s, starting from rest under the actions o a constant force, is directly proportional to;

A

m^0

Does not depend upon mass

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31
Q

When force and displacement are in the same direction, the kinetic energy of the body.

A

Increases

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32
Q

A truck and a car are moving with equal velocity. On applying brakes, both will stop after a certain distance, then?

A

The car will cover less distance before stopping

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33
Q

Potential energy per unit volume is given by:

A

ρgh

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34
Q

A body is falling from a height h. After it has fallen a height of h/2, it will possess

A

Hal Potential and Half Kinetic Energy

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35
Q

Energy stored in the spring of which is:

A

Elastic Potential Energy

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36
Q

Initially, four identical uniform blocks, each of mass m and thickness h, are spread on a table, work require to stack them on one another is;

A 
6 mgh
(W= n(n-1)/2 mgh)
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37
Q

A stone is thrown up from the surface of earth when it reaches maximum height. Its total energy is equal to;

A

mgh

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38
Q

Energy consumed by a 60-watt bulb in 2 minutes is equal to;

A

7.2 kilojoules

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39
Q

The consumption of energy by a 60-watt bulb in 2 seconds is:

A

120J

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40
Q

100 Joules work has been done by an agency in 10 seconds. What is the power of energy?

A

10 watt

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41
Q

A 500N force is applied to an object and it moves with a velocity of 10m/s.If the value of power is 2500watt.Then what will be the angle between force and displacement?

A

60°

cos 60°=1/2

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42
Q

The time taken by an engine of power 10kW to lift a mass of 200kg to the height of 40 m is:

A 
8 sec
(P=mgh/t)
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43
Q

To travel at a constant speed, a car engine provides 24kW of useful power. The driving force on the car is 600N. At what seed does it travel?

A

40 m/s

P=Fv

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44
Q

A force of 1000 N is needed to lift the hook of a crane at a steady velocity The crane is then used to lift a load of mass 1000kg at a velocity of 0.50m/s.How much much of the power developed by the motor of the crane is used in lifting the hook and the load?

A

5.5 kW

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45
Q

The power output of a lamp is 6W. How much energy does the lamp give out in 2 minutes?

A

720 J

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46
Q

A man M1 of mass 80kg runs up a staircase in 15 sec. Another man M2 also of mass 80kg runs up the same staircase in 20 sec. The ratio o the power developed by them will be:

A

4/3

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47
Q

An engine pumps out 100kg of water through a height of 10 m in 5s. Given that the efficiency of the engine is 60%m what is the power of the efficiency?

A

3.3 kW

%age change in any quanitity= {(1±n)^k -1} x 100

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48
Q

An engine pumps up 40kg of water through a height of 10m in 5 sec. The water comes out vertically upwards with a velocity of 3m/s. What is the power of the engine in kilowatts?

A

1.2 kW

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49
Q

An elevator’s motor produces 3000 W power. The speed with which it can lift a 1000kg load is;

A

0.306 m/s

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50
Q

The power needed to lift a mass of 5000g to a height of 1m in 2 seconds is:

A

24.5 watt

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51
Q

An engine pulls a car of mass 1500kg on a level road at a constant speed of 5 m/s.If the frictional force is 500N, what power does the engine generates?

A

2.5 kW

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52
Q

Work done on a body equals the change in its ____ energy.

A

Total

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53
Q

If a certain force acts on an object and changes its kinetic energy from 65J to 130J. Then work done by the force will be:

A

651J
(According to Work-Energy Principle,
Work Done=Kinetic Energy

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54
Q

The amount of work required to stop a moving object is equal to;

A

The kinetic energy of the object

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55
Q

The work-energy principle is valid for:

A

All types of Energies

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56
Q

The mathematical form of work energy principle is:

A

Fd= 1/2 mvf^2 - 1/2 mvi^2

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57
Q

Unit of energy:

A

Joule

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58
Q

Work done will be maximum if the angle between the force F and displacement d is:

A

0°

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59
Q

A field in which the work is done in moving a body along a closed path is zero is called:

A

Conservative Field

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60
Q

When a force is parallel to the direction of motion of the body, then work done is:

A

Maximum

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61
Q

If a body with a mass of 2kg is raised vertically through 2m, then the work done will be:

A

39.2 J

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62
Q

The relation between horsepower and watt is:

A

1 hp = 746 watt

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63
Q

The slope of the work time graph is equal to:

A

Power

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64
Q

The consumption of energy by a 60-watt bulb in 2 sec is:

A

120J

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65
Q

A man lifts vertically a weight of 40kg through 1m in 10sec, while a child lifts vertically a weight of 10kg through a distance of 1m in 1s. What will be the correct inference?

A

Man does more work than the child

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66
Q

The area under the force-displacement graph represents:

A

Work Done

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67
Q

When can one say that work is done on the body:

A

When there is an increase in energy because of mechanical influence

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68
Q

The work done on an object does not depend upon the:

A

The initial velocity of the object

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69
Q

A machine does 2500J of work in 1min. What is the power developed by the machine?

A

42W

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70
Q

A moving car possesses:

A

Mechanical Energy

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71
Q

The interconversion of matter and energy is predicted by:

A

Einstein

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72
Q

A bus weighing 12kN has a speed of 20 m/s. Its kinetic energy is;

A

240 kJ

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73
Q

According to the law of conservation of energy:

A

➡Energy cant be destroyed
➡Energy can’t be created
➡Energy can be transformed from one form to the other

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74
Q

kWh is the unit of:

A

Energy

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75
Q

An object that has potential energy has this energy because of its:

A

Location

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76
Q

The power of an agent is:

A

➡The rate of generation of energy
➡The rate of transfer of energy
➡The rate of consumption of energy

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77
Q

Unit of energy:

A

➡Joule
➡Calorie
➡KiloJoule

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78
Q

Power delivered by the water pump on lifting:

A

P=mgh/t

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79
Q

2kg mass is uplifted by the machine through the height o 200m for 10 sec. Calculate the power delivered to the load.

A

400W

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80
Q

Light body A and heavy body B have equal K.E of translation. The:

A

B has larger momentum than A

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81
Q

The Energy required to accelerate a car from 10ms to 20 m/s compared with that required to accelerate is from 0 to 10 is:

A

Four times

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82
Q

The kinetic energy of a body is 1000J, its momentum decrease by 50% then the kinetic energy of that body becomes:

A

750J

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83
Q

Work done will be maximum. If the angle between the force F and displacement is:

A

0°

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84
Q

Which of the following have the same dimension:

A

➡Energy

➡Work

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85
Q

The slope of the work time graph is equal to:

A

Power

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86
Q

If the velocity is doubled then:

A

➡Momentum increases 2 times

➡K.E increases 4 times

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87
Q

What is the average power required to lift a mass of 100kg to a height of 50m in 50 seconds?

A

980

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88
Q

When one can say that work is done on the body:

A

When there is an increase in energy because of mechanical influence

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89
Q

In the case of negative work, the angle between the force and displacement is:

A

180°

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90
Q

A car travels at a constant speed of 15 m/s. The car’s engine produces a 4000N pushing force in order to keep the speed constant. How much power is developed by the engine?

A

60000W

91
Q

If a pump can lift 200 kg of water through a height of 6m in 10 seconds, then its power is;

A

1200 watts

92
Q

As the rain falls, the potential energy changes to:

A

Kinetic Energy

93
Q

I the linera momentum of the oject is increased by 0.1%, then the kinetic energy is increased by:

A

0.2%

94
Q

Work done by a conservative force is:

A

Reversible

95
Q

A particle of mass 2kg is in a circular motion with a velocity of 5 m/s2, and the radius of the path is 2m. What will be the work done by the centrifugal force in the half cycle?

A

0

96
Q

A force F= (0.5x +10)N acts on a particle, Calculate the work done by the force in displacing the particle to x=0 to x=2m

A

21J

97
Q

A constant force of F = (i-2j-3k) causes a displacement d = (2i-5j+k), what will be the net work done if F in N and displacement is in meter

A

9J

98
Q

A gardener moves a lawn roller through a distance of 50m. The applied force is 50N inclined at 60 degrees of direction of motion which will be the work done by the gardener.

A

1250J

99
Q

What is the kinetic energy of body 5 kg and momentum 15 kg.m/sec.

A

22.5 J

100
Q

Work done by the non-conservative forces is;

A

Non-Reversible

101
Q

Two Forces o 1 = 5N and F2=15n are working on a body in opposite direction. If body displaced by 5m in direction o net force, what will be the work done by F1:

A

75J

102
Q

When a spring is strecthced, work done by stretching force is;

A

Positive

103
Q

K.E of the body is increased by 44%, what is the percentage increase in the momentum:

A

20%

104
Q

Work done on a ceiling fan by gravity is:

A

Zero

105
Q

A body of mass of 10kg is travelling with a uniform speed of 5 m/s. Its kinetic energy is;

A

125J

106
Q

When a body moves vertically upward, the work done will be;

A

Negative

107
Q

A body moves a distance of 10m along a straight line under the action of 5N force. If work done is 25J, then the angle between the force and direction of motion of the body will be:

A

60°

108
Q

A force F=7-2x+3x^2 is applied on a 2kg body, and work done to displace the body from x=0 to x=5 m

A

200J

109
Q

Work done by friction is always:

A

Negative

110
Q

When a man walks on a surface horizontally with constant velocity. work done by:

A

Gravity is zero

111
Q

When brakes are applied to a moving vehicle, the work done by the braking system is:

A

Negative

112
Q

A horse is pulling a cart of mass of 50 kg on the horizontal direction, if the distance travelled is 20m then what w

A

0

113
Q

Work done by a conservative force in the complete cycle is:

A

Zero

114
Q

Two forces of F1=5N and F2=15N are working on a body in opposite directions. If the body is displaced by 5m in direction of the net force, what will be the work done by F(net)

A

75J

115
Q

A 4kg eagle picks up a 75g of snake and raises it 2.5 m from the ground to a branch. What is the work done to raise the bird’s own centre of mass to the branch?

A

1.875J

116
Q

If force is F=4i -2j and displacement is d3i +4j, the work done will be:

A

4J

117
Q

A man pushes a wall and fails to displace it, he does

A

No work at all

118
Q

Consider a drop o water o mass of 1 g falling from a height o 1 km. It hits the ground with a speed of 50m/s, then works done by resistive force of air is:

A

-8.75J

119
Q

When work done by force of gravity is negative:

A

Potential Energy Increases

120
Q

If the speed of the body is doubled, then:

A

Momentum Doubled

121
Q

_____ work on an arbitrary system means a transfer of energy to the system.

A

Positive

122
Q

A stone of mass 1 kg dropped from a height of 10m with the speed of 14 m/s, approximate kinetic energy is;

A

10J

123
Q

A man standing in a bus and pushing the wall of the bus in direction of motion. Work done by the man is:

A

Zero

124
Q

The kinetic energy of the body is increased by 21%. What is the percentage change in the linear momentum of the body?

A

10

125
Q

Work done can be calculated by taking:

A

Dot Product of Force and Displacement

126
Q

A body of mass 10kg is moved parallel to the ground, through a distance of 2m.The work done against a gravitational force is:

A

Zero

127
Q

A constant force of F=(i-2j-3k) causes a displacement d= (2i-5j+k), what will be the net work done if F and N and displacement is in meter

A

9J

128
Q

A constant force of 10N is applied on a body which causes displacement of 12cm what will be the work done:

A

12J

129
Q

Work done by friction:

A

Can be negative

130
Q

If a proter is carrying a load and waiting for the arrival of the train then work done by the porter is:

A

Zero

131
Q

A cyclist comes to a skidding stop in 10m, the force on the cycle due to the road is 200N and opposite to the motion, how much work does the road do on the cycle:

A

-2000J

132
Q

Moon is revolving around the earth, work done by the earth on the moon is;

A

Zero

133
Q

A constant force of 20N is applied in the horizontal direction and the distance travelled in the direction of force is 5, then work done is:

A

100J

134
Q

A body of mass 2kg is raised vertically raised by 2m, then work done will be;

A

39.2 J

135
Q

A variable force F=X is applied what will be the work done in moving the particle from X=0 to1

A

0.5 J

136
Q

A bullet of mass of 10g leaves a rifle at an initial velocity of 1000m/s and strikes the earth at the same level with a velocity of 500 m/s. The work in overcoming the resistance of air will be:

A

3750J

137
Q

A bullet fired from a gun can pierce a target due to;

A

Kinetic Energy

138
Q

A man moves a roller through a distance of 20m. 10N of applied force is inclined at 60 degrees of the direction of motion what will be the work done by the man:

A

100 J

139
Q

Work is done by the applying force when:

A

Applied force-generated motion

140
Q

What is the SI unit of work;

A

Joule

141
Q

In the case of harmonic oscillator total energy remains:

A

Constant

142
Q

In the case of a simple pendulum total energy remains;

A

Constant

143
Q

A bullet of mass 5x10^-5 has a velocity of 200 m/s, kinetic energy of the bullet is:

A

1 J

144
Q

Which of the following is not a conservative force is:

A

Friction

145
Q

A field in which work done in a moving a body along the close path is zero called:

A

Conservative field

146
Q

A spring having a spring constant of 10 N/m2 is stretched to 5m, what will be the work done;

A

125 J

147
Q

An object is displaced from point A (0,1,1) m to point B (1,4,3) m under a constant force F=(i+2j+3k). Find the work done by this force in this process

A

13 J

148
Q

A man holds a bucket by applying force 10N, then moves a horizontal distance of 5m and vertical distance of 10m, find out the net work done:

A

100 J

149
Q

The K.E of a body of mass 2kg and momentum of 2Ns is;

A

1J

150
Q

Two masses 1g and 4g are moving with equal kinetic energies. The ratio of the magnitudes of their linear momentum is:

A

1:2

151
Q

Work is a:

A

Scalar Quantity

152
Q

Work done is said to be negative if force and displacement are;

A

Anti-Parallel

153
Q

A constant force of 10N is applied in the horizontal direction and the distance travelled in the direction of force is 2m, then work done is:

A

20 J

154
Q

Work is said to be done when a body moves through a certain distance by the action of:

A

Force

155
Q

A force of F=(1+y) N is acting in the y direction, work done by this force to move the particle from y=0 to y=1m

A

1.5 J

156
Q

An object is displaced from point A (2,3,4) m to point B (1,2,3) m under a constant force F=(2i+3j+4k). Find the work done by this force in this process:

A

-9 J

157
Q

Work done by the centripetal force on a body moving in a circle is zero because:

A

The body move right angle to F

158
Q

For a particular displacement how is the work done related to time:

A

Independent of time

159
Q

At which angle work done is maximum:

A

0°

160
Q

When the direction of the force and displacement are opposite, work done is;

A

Negative

161
Q

When the momentum of a body is increased by 200%, its kinetic energy increases by:

A

800%

162
Q

When a force is parallel to the direction of motion of the body, the work done is:

A

Maximum

163
Q

If a horse pulls a cart, work done by the horse is;

A

Positive

164
Q

A particle moves from point P(1,2,3) to Q(2,1,4) under the action of a constant force F=(2i+j+k), work done by the force is;

A

2 J

165
Q

If momentum is increased by 20%, then K.E increases by:

A

0.44

166
Q

1 joule is equal to;

A

10^7 erg

167
Q

A 4kg eagle picks up a 75g and raises it 2.5m from the ground to a branch. What is the work done by the eagle on the snake:

A

1.875 J

168
Q

A stone of 1kg is thrown upwards it reaches a max height of 5m, work done by the gravity is:

A

-49 J

169
Q

The atmosphere around the earth is held by:

A

Gravity

170
Q

A disc of radius 2m and mass of 100 kg rolls on a horizontal force, and its centre of mass has a speed of 2cm/s, how much work is needed to stop it;

A

0.02 J

171
Q

Work done can be calculated by taking:

A

The dot product of force and displacement

172
Q

A force of F=20 +10y N is acting in the y direction, work done by this force to move the article from y=0 to y=1m

A

25 J

173
Q

Effect of work is equal to;

A

Change in kinetic energy

174
Q

If two point charges of charge q1 and q2 are placed at distance D. The force between them is proportional to;

A

1/d^2

175
Q

Which of the following vector is perpendicular to the vector A=2i +3j +4k

A

i + 2j - 2k

176
Q

A ball is released from the top of the tower, and the ratio of work done by the gravity in the first, second and third second of the motion

A

1:3:5

177
Q

At which angle work done is minimum;

A

90°

178
Q

A force of F=20 + 10y N is acting in the y direction, work done by this force to move the particle from y=0 to y=1m

A

25 J

179
Q

A constant force F=2i + 3j + 4k is applied to a body what will be the work done to move a body 5m in the z-direction

A

20 J

180
Q

1 joule is equal to;

A

10^7 erg

181
Q

A force 2i + j has moved its point of application from (2,3) to (6,5). What is work done?

A

+10

182
Q

100 joules of work have been done by an agency in 10 seconds. What is the power of agency?

A

10 watt

183
Q

Work done on a body equals the change in its ___ energy

A

➡Total
➡Kinetic
➡Potential

184
Q

If a certain force acts on an object and changes its kinetic energy from 65 J to 130 J, then work done by the force will be;

A

65 J

Work Done = ΔK.E

185
Q

The consumption of energy by a 6-watt bulb in 2 seconds is:

A

120J

186
Q

Which one of the following is a non-conservative force?

A

Frictional Force

187
Q

If velocity is double, then:

A

➡Momentum increases 2 times

➡K.E increases 4 times

188
Q

The heat energy dissipated by 40 watts also in one hour is:

A

144000J

W=P x t

189
Q

The gravitational potential energy per unit mass is called:

A

Gravitational Potential

190
Q

A 6.0 kg block is released from the rest 80m above the ground. When it has fallen 60m its kinetic energy is approxiamatly:

A

3500 J

191
Q

Potential energy per unit volume is given by;

A

ρgh

192
Q

Work done will be zero if the angle between Force and displacement is:

A

270°

cos270°=0°

193
Q

If mass ‘m’ is dropped from height ‘h’ vertically, F is the force of friction during downward motion and ‘v’ is the velocity at the bottom, the following equation will be held;

A

mgh = 1/2 mv^2 + fh

194
Q

At what angle work done will be maximum:

A

0°

195
Q

Which one of the following is a greater work?

A

-1000J

196
Q

A man of mass of 60 kg climbs up a 20m long staircase to the top of a building 10m high. What is their work done by him:

A

6 kJ

197
Q

When a force retards the motion of a body the work done is;

A

Negative

198
Q

An engine pumps out 40kg of water in one second. The water comes out vertically upwards with a velocity of 3m/s, the power of the engine in kilo watt is;

A

1.2 kW

199
Q

Two boys weighing in the ratio 4:5 go stair taking time in the ratio of 5;4. The ratio of their power is;

A

16/25

200
Q

Energy consumed by 60- watt bulb in minutes is equal to:

A

7.2 kilojoules

201
Q

A stone of mass 2.0 kg is dropped from a rest position 5.0 m above the ground. What is its velocity at a height of 3.0 m above the ground?

A

6.3 m/s

vf = √2g (h2 -h1

202
Q

The rate at which work is being done is called;

A

Power

203
Q

A man has a mass of 80 kg. He ties himself to one end of the rope which passes over a single fixed pulley. He pulls on the other end of the rope to lift himself up at an average speed of 50 cm/s. What is the average useful power at which he is working?

A

0.39 kW

P=mgv

204
Q

If the momentum of a body decreases by 20%, the percentage decreases in K.E will be:

A

36%

%age change in any quantity= {(1±n)^k -1 } x 100

205
Q

A man carries a 1 kg body 10m horizontally on level ground. The work zone by the:

A

0 J

206
Q

An automobile is moving forwards with uniform velocity due to the force exerted by its engine. If that force is double with velocity remaining constant what happens to its total power?

A

It is doubled

207
Q

Which of the following statement shows that no work is done?

A

The moon orbiting the earth

208
Q

A 1.75 m heightened weight-lifter raises weights with a mass of 50kg to a height of 5m above his head. How much work is being done by him?

A

1225J

209
Q

When the speed of your car is halved, by what factor does its kinetic energy decrease?

A

1/4

210
Q

Which of the following force is a non-conservative force?

A

Frictional Force

211
Q

The area under the force-displacement graph gives us;

A

Work

212
Q

Kilowatt- hour is unit o;

A

Electric energy

213
Q

A field in which the work is done in a moving body along a closed path is zero is called:

A

Conservative field

214
Q

A field in which the work done in a moving body along a closed path is zero is called:

A

Conservative Field

215
Q

When a force is parallel to the direction of motion of the body, then work done on the body is:

A

Maximum

216
Q

If a body of mass 2kg is raised vertically through 2m, then the work done will be;

A

39.2 j

217
Q

The relation between horsepower and watt is;

A

1 hp = 746 watts

218
Q

The area under the force-displacement graph represents:

A

Work done

219
Q

A machine does 2500 J of work in 1min. What is the power developed by the machine?

A

42 W

220
Q

A moving car possesses:

A

Mechanical Energy

221
Q

kWh is the unit of:

A

Energy

222
Q

2 kg of mass is uplifted by the machine through the height of 200m for 10 sec. Calculate the power delivered to the load

A

400W

223
Q

Light body A and heavy body B have equal K.E translation. Then

A

B has larger momentum than A

PHYSICS (13 decks)

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