UNIT#02 WORK AND ENERGY Flashcards
(223 cards)
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)
2
Q
What sort of energy does a flying bird possess?
A
➡Potential Energy
➡Kinetic Energy
3
Q
When the velocity of an aeroplane is doubled, the momentum ____.
A
Is conserved
(as the momentum of air also increases)
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)
5
Q
A bullet fired from a gun can pierce a target due to its
A
Kinetic Energy
6
Q
Kinetic energy with any reference must be:
A
Positive
7
Q
At what angle, work done will be maximum?
A
0°
8
Q
Which one of the following is a greater work?
A
-1000J
9
Q
Work done will be zero if the angle between Force and Displacement is;
A
270°
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)
11
Q
At what angle the work done will be half of its maximum value:
A
60°
12
Q
A man pushes a wall with 50N and it displaces it zero m, his work done is:
A
No work
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
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
15
Q
A force of 3i+2j+4k N gives a displacement of 10jm. The work done is:
A
20J
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°
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
18
Q
Suppose the force and displacement of a particle in the direction of force are doubled. Work would be:
A
4 times
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
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
21
Q
If velocity is double, then:
A
Momentum increases 2 times and K.E increases 4 times
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
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
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
25
The momentum and kinetic energy of a ball are numerically equal. The numerical velocity is;
2 m/s
26
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:
270J
27
Car X is travelling at half the speed of ar Y. Car X has twice the mass of car Y. Which statement is correct?
Car X has half the kinetic energy of car Y
28
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:
1:2
29
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:
486J
30
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;
m^0
(Does not depend upon mass)
31
When force and displacement are in the same direction, the kinetic energy of the body.
Increases
32
A truck and a car are moving with equal velocity. On applying brakes, both will stop after a certain distance, then?
The car will cover less distance before stopping
33
Potential energy per unit volume is given by:
ρgh
34
A body is falling from a height h. After it has fallen a height of h/2, it will possess
Hal Potential and Half Kinetic Energy
35
Energy stored in the spring of which is:
Elastic Potential Energy
36
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;
6 mgh
(W= n(n-1)/2 mgh)
37
A stone is thrown up from the surface of earth when it reaches maximum height. Its total energy is equal to;
mgh
38
Energy consumed by a 60-watt bulb in 2 minutes is equal to;
7.2 kilojoules
39
The consumption of energy by a 60-watt bulb in 2 seconds is:
120J
40
100 Joules work has been done by an agency in 10 seconds. What is the power of energy?
10 watt
41
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?
60°
(cos 60°=1/2)
42
The time taken by an engine of power 10kW to lift a mass of 200kg to the height of 40 m is:
8 sec
(P=mgh/t)
43
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?
40 m/s
(P=Fv)
44
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?
5.5 kW
45
The power output of a lamp is 6W. How much energy does the lamp give out in 2 minutes?
720 J
46
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:
4/3
47
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?
3.3 kW
%age change in any quanitity= {(1±n)^k -1} x 100
48
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?
1.2 kW
49
An elevator's motor produces 3000 W power. The speed with which it can lift a 1000kg load is;
0.306 m/s
50
The power needed to lift a mass of 5000g to a height of 1m in 2 seconds is:
24.5 watt
51
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?
2.5 kW
52
Work done on a body equals the change in its ____ energy.
Total
53
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:
651J
(According to Work-Energy Principle,
Work Done=Kinetic Energy
54
The amount of work required to stop a moving object is equal to;
The kinetic energy of the object
55
The work-energy principle is valid for:
All types of Energies
56
The mathematical form of work energy principle is:
Fd= 1/2 mvf^2 - 1/2 mvi^2
57
Unit of energy:
Joule
58
Work done will be maximum if the angle between the force F and displacement d is:
0°
59
A field in which the work is done in moving a body along a closed path is zero is called:
Conservative Field
60
When a force is parallel to the direction of motion of the body, then work done is:
Maximum
61
If a body with a mass of 2kg is raised vertically through 2m, then the work done will be:
39.2 J
62
The relation between horsepower and watt is:
1 hp = 746 watt
63
The slope of the work time graph is equal to:
Power
64
The consumption of energy by a 60-watt bulb in 2 sec is:
120J
65
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?
Man does more work than the child
66
The area under the force-displacement graph represents:
Work Done
67
When can one say that work is done on the body:
When there is an increase in energy because of mechanical influence
68
The work done on an object does not depend upon the:
The initial velocity of the object
69
A machine does 2500J of work in 1min. What is the power developed by the machine?
42W
70
A moving car possesses:
Mechanical Energy
71
The interconversion of matter and energy is predicted by:
Einstein
72
A bus weighing 12kN has a speed of 20 m/s. Its kinetic energy is;
240 kJ
73
According to the law of conservation of energy:
➡Energy cant be destroyed
➡Energy can't be created
➡Energy can be transformed from one form to the other
74
kWh is the unit of:
Energy
75
An object that has potential energy has this energy because of its:
Location
76
The power of an agent is:
➡The rate of generation of energy
➡The rate of transfer of energy
➡The rate of consumption of energy
77
Unit of energy:
➡Joule
➡Calorie
➡KiloJoule
78
Power delivered by the water pump on lifting:
P=mgh/t
79
2kg mass is uplifted by the machine through the height o 200m for 10 sec. Calculate the power delivered to the load.
400W
80
Light body A and heavy body B have equal K.E of translation. The:
B has larger momentum than A
81
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:
Four times
82
The kinetic energy of a body is 1000J, its momentum decrease by 50% then the kinetic energy of that body becomes:
750J
83
Work done will be maximum. If the angle between the force F and displacement is:
0°
84
Which of the following have the same dimension:
➡Energy
➡Work
85
The slope of the work time graph is equal to:
Power
86
If the velocity is doubled then:
➡Momentum increases 2 times
➡K.E increases 4 times
87
What is the average power required to lift a mass of 100kg to a height of 50m in 50 seconds?
980
88
When one can say that work is done on the body:
When there is an increase in energy because of mechanical influence
89
In the case of negative work, the angle between the force and displacement is:
180°
90
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?
60000W
91
If a pump can lift 200 kg of water through a height of 6m in 10 seconds, then its power is;
1200 watts
92
As the rain falls, the potential energy changes to:
Kinetic Energy
93
I the linera momentum of the oject is increased by 0.1%, then the kinetic energy is increased by:
0.2%
94
Work done by a conservative force is:
Reversible
95
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?
0
96
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
21J
97
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
9J
98
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.
1250J
99
What is the kinetic energy of body 5 kg and momentum 15 kg.m/sec.
22.5 J
100
Work done by the non-conservative forces is;
Non-Reversible
101
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:
75J
102
When a spring is strecthced, work done by stretching force is;
Positive
103
K.E of the body is increased by 44%, what is the percentage increase in the momentum:
20%
104
Work done on a ceiling fan by gravity is:
Zero
105
A body of mass of 10kg is travelling with a uniform speed of 5 m/s. Its kinetic energy is;
125J
106
When a body moves vertically upward, the work done will be;
Negative
107
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:
60°
108
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
200J
109
Work done by friction is always:
Negative
110
When a man walks on a surface horizontally with constant velocity. work done by:
Gravity is zero
111
When brakes are applied to a moving vehicle, the work done by the braking system is:
Negative
112
A horse is pulling a cart of mass of 50 kg on the horizontal direction, if the distance travelled is 20m then what w
0
113
Work done by a conservative force in the complete cycle is:
Zero
114
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)
75J
115
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?
1.875J
116
If force is F=4i -2j and displacement is d3i +4j, the work done will be:
4J
117
A man pushes a wall and fails to displace it, he does
No work at all
118
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:
-8.75J
119
When work done by force of gravity is negative:
Potential Energy Increases
120
If the speed of the body is doubled, then:
Momentum Doubled
121
_____ work on an arbitrary system means a transfer of energy to the system.
Positive
122
A stone of mass 1 kg dropped from a height of 10m with the speed of 14 m/s, approximate kinetic energy is;
10J
123
A man standing in a bus and pushing the wall of the bus in direction of motion. Work done by the man is:
Zero
124
The kinetic energy of the body is increased by 21%. What is the percentage change in the linear momentum of the body?
10
125
Work done can be calculated by taking:
Dot Product of Force and Displacement
126
A body of mass 10kg is moved parallel to the ground, through a distance of 2m.The work done against a gravitational force is:
Zero
127
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
9J
128
A constant force of 10N is applied on a body which causes displacement of 12cm what will be the work done:
12J
129
Work done by friction:
Can be negative
130
If a proter is carrying a load and waiting for the arrival of the train then work done by the porter is:
Zero
131
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:
-2000J
132
Moon is revolving around the earth, work done by the earth on the moon is;
Zero
133
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:
100J
134
A body of mass 2kg is raised vertically raised by 2m, then work done will be;
39.2 J
135
A variable force F=X is applied what will be the work done in moving the particle from X=0 to1
0.5 J
136
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:
3750J
137
A bullet fired from a gun can pierce a target due to;
Kinetic Energy
138
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:
100 J
139
Work is done by the applying force when:
Applied force-generated motion
140
What is the SI unit of work;
Joule
141
In the case of harmonic oscillator total energy remains:
Constant
142
In the case of a simple pendulum total energy remains;
Constant
143
A bullet of mass 5x10^-5 has a velocity of 200 m/s, kinetic energy of the bullet is:
1 J
144
Which of the following is not a conservative force is:
Friction
145
A field in which work done in a moving a body along the close path is zero called:
Conservative field
146
A spring having a spring constant of 10 N/m2 is stretched to 5m, what will be the work done;
125 J
147
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
13 J
148
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:
100 J
149
The K.E of a body of mass 2kg and momentum of 2Ns is;
1J
150
Two masses 1g and 4g are moving with equal kinetic energies. The ratio of the magnitudes of their linear momentum is:
1:2
151
Work is a:
Scalar Quantity
152
Work done is said to be negative if force and displacement are;
Anti-Parallel
153
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:
20 J
154
Work is said to be done when a body moves through a certain distance by the action of:
Force
155
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
1.5 J
156
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:
-9 J
157
Work done by the centripetal force on a body moving in a circle is zero because:
The body move right angle to F
158
For a particular displacement how is the work done related to time:
Independent of time
159
At which angle work done is maximum:
0°
160
When the direction of the force and displacement are opposite, work done is;
Negative
161
When the momentum of a body is increased by 200%, its kinetic energy increases by:
800%
162
When a force is parallel to the direction of motion of the body, the work done is:
Maximum
163
If a horse pulls a cart, work done by the horse is;
Positive
164
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;
2 J
165
If momentum is increased by 20%, then K.E increases by:
0.44
166
1 joule is equal to;
10^7 erg
167
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:
1.875 J
168
A stone of 1kg is thrown upwards it reaches a max height of 5m, work done by the gravity is:
-49 J
169
The atmosphere around the earth is held by:
Gravity
170
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;
0.02 J
171
Work done can be calculated by taking:
The dot product of force and displacement
172
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
25 J
173
Effect of work is equal to;
Change in kinetic energy
174
If two point charges of charge q1 and q2 are placed at distance D. The force between them is proportional to;
1/d^2
175
Which of the following vector is perpendicular to the vector A=2i +3j +4k
i + 2j - 2k
176
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
1:3:5
177
Q
At which angle work done is minimum;
90°
178
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
25 J
179
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
20 J
180
1 joule is equal to;
10^7 erg
181
A force 2i + j has moved its point of application from (2,3) to (6,5). What is work done?
+10
182
100 joules of work have been done by an agency in 10 seconds. What is the power of agency?
10 watt
183
Work done on a body equals the change in its ___ energy
➡Total
➡Kinetic
➡Potential
184
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;
65 J
(Work Done = ΔK.E)
185
The consumption of energy by a 6-watt bulb in 2 seconds is:
120J
186
Which one of the following is a non-conservative force?
Frictional Force
187
If velocity is double, then:
➡Momentum increases 2 times
➡K.E increases 4 times
188
The heat energy dissipated by 40 watts also in one hour is:
144000J
(W=P x t)
189
The gravitational potential energy per unit mass is called:
Gravitational Potential
190
A 6.0 kg block is released from the rest 80m above the ground. When it has fallen 60m its kinetic energy is approxiamatly:
3500 J
191
Potential energy per unit volume is given by;
ρgh
192
Work done will be zero if the angle between Force and displacement is:
270°
(cos270°=0°)
193
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;
mgh = 1/2 mv^2 + fh
194
At what angle work done will be maximum:
0°
195
Which one of the following is a greater work?
-1000J
196
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:
6 kJ
197
When a force retards the motion of a body the work done is;
Negative
198
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;
1.2 kW
199
Two boys weighing in the ratio 4:5 go stair taking time in the ratio of 5;4. The ratio of their power is;
16/25
200
Energy consumed by 60- watt bulb in minutes is equal to:
7.2 kilojoules
201
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?
6.3 m/s
(vf = √2g (h2 -h1)
202
The rate at which work is being done is called;
Power
203
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?
0.39 kW
(P=mgv)
204
If the momentum of a body decreases by 20%, the percentage decreases in K.E will be:
36%
(%age change in any quantity= {(1±n)^k -1 } x 100)
205
A man carries a 1 kg body 10m horizontally on level ground. The work zone by the:
0 J
206
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?
It is doubled
207
Which of the following statement shows that no work is done?
The moon orbiting the earth
208
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?
1225J
209
When the speed of your car is halved, by what factor does its kinetic energy decrease?
1/4
210
Which of the following force is a non-conservative force?
Frictional Force
211
The area under the force-displacement graph gives us;
Work
212
Kilowatt- hour is unit o;
Electric energy
213
A field in which the work is done in a moving body along a closed path is zero is called:
Conservative field
214
A field in which the work done in a moving body along a closed path is zero is called:
Conservative Field
215
When a force is parallel to the direction of motion of the body, then work done on the body is:
Maximum
216
If a body of mass 2kg is raised vertically through 2m, then the work done will be;
39.2 j
217
The relation between horsepower and watt is;
1 hp = 746 watts
218
The area under the force-displacement graph represents:
Work done
219
A machine does 2500 J of work in 1min. What is the power developed by the machine?
42 W
220
A moving car possesses:
Mechanical Energy
221
kWh is the unit of:
Energy
222
2 kg of mass is uplifted by the machine through the height of 200m for 10 sec. Calculate the power delivered to the load
400W
223
Light body A and heavy body B have equal K.E translation. Then
B has larger momentum than A
