Work, Energy and Power-1 Practice Questions - DPP for NEET

 Page 1


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A body is acted upon by a force 
ˆ ˆˆ
F i 2j 3k =-++
r
. The work
done by the force in displacing it from (0,0,0) to (0,0,4m) will
be -
(a) 12 J (b) 10 J
(c) 8 J (d) 6 J
Q.2 The work done in pulling a body of mass 5 kg along an inclined
plane (angle 60º) with coefficient of friction 0.2 through 2
m, will be -
(a) 98.08 J (b) 94.08 J
(c) 90.08 J (d) 91.08 J
Q.3 A force F
r
 = (7 – 2x + 3x
2
) N is applied on a 2 kg mass
which displaces it from x = 0 to x = 5 m. Work done in
joule is -
(a) 70 (b) 270 (c) 35 (d) 135
Q.4 An automobile of mass m accelerates from rest. If the engine
supplies a constant power P , the velocity at time t is given by -
(a) v = 
Pt
m
(b) v = 
2Pt
m
(c)
Pt
m
(d)
2Pt
m
Q.5 In the above question, the position (s) at time (t) is given by -
(a)
2Pt
t
m
æö
ç÷
èø
(b)
1/2
8P
9m
æö
ç÷
èø
t 
3/2
(c)
1/2
9P
8m
æö
ç÷
èø
t
1/2
(d)
1/2
8P
t
9m
æö
ç÷
èø
Page 2


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A body is acted upon by a force 
ˆ ˆˆ
F i 2j 3k =-++
r
. The work
done by the force in displacing it from (0,0,0) to (0,0,4m) will
be -
(a) 12 J (b) 10 J
(c) 8 J (d) 6 J
Q.2 The work done in pulling a body of mass 5 kg along an inclined
plane (angle 60º) with coefficient of friction 0.2 through 2
m, will be -
(a) 98.08 J (b) 94.08 J
(c) 90.08 J (d) 91.08 J
Q.3 A force F
r
 = (7 – 2x + 3x
2
) N is applied on a 2 kg mass
which displaces it from x = 0 to x = 5 m. Work done in
joule is -
(a) 70 (b) 270 (c) 35 (d) 135
Q.4 An automobile of mass m accelerates from rest. If the engine
supplies a constant power P , the velocity at time t is given by -
(a) v = 
Pt
m
(b) v = 
2Pt
m
(c)
Pt
m
(d)
2Pt
m
Q.5 In the above question, the position (s) at time (t) is given by -
(a)
2Pt
t
m
æö
ç÷
èø
(b)
1/2
8P
9m
æö
ç÷
èø
t 
3/2
(c)
1/2
9P
8m
æö
ç÷
èø
t
1/2
(d)
1/2
8P
t
9m
æö
ç÷
èø
2
DPP/ P 12
Q.6 A particle moving in a straight line is acted by a force, which
works at a constant rate and changes its velocity from u to
v in passing over a distance x. The time taken will be -
(a) x = 
22
vu
vu
-
+
(b) x 
22
vu
vu
æö +
ç÷
èø
+
(c)
3
2
 (x) 
22
33
vu
vu
æö
-
ç÷
- èø
(d) x 
v
u
æö
ç÷
èø
Q.7 A chain of linear density 3 kg /m and length 8 m is lying on
the table with 4 m of chain hanging from the edge. The
work done in lifting the chain on the table will be -
(a) 117.6 J (b) 235.2 J (c) 98 J (d) 196 J
Q.8 The work done in lifting water from a well of depth 6 m
using a bucket of mass 0.5 kg and volume 2 litre, will be-
(a) 73.5 J (b) 147 J (c) 117. 6 J (d) 98 J
Q.9 An object of mass 5 kg falls from rest through a vertical
distance of 20 m and reaches a velocity of 10 m/s. How
much work is done by the push of the air on the object ?
(g = 10 m/s
2
).
(a) 350 J (b) 750 J (c) 200 J (d) 300 J
Q.10 A boy pulls a 5 kg block 20 metres along a horizontal sur-
face at a constant speed with a force directed 45° above
the horizontal. If the coefficient of kinetic friction is 0.20,
how much work does the boy do on the block?
(a) 163.32 J (b) 11.55 J
(c) 150 J (d) 115 J
Q.11 A uniform chain is held on a frictionless table with one-
fifth of its length hanging over the edge. If the chain has a
length l and a mass m, how much work is required to pull
the hanging part back on the table ?
(a) mg l / 10 (b) mg l / 5
(c) mg l / 50 (d) mg l / 2
Q.12 A bus of mass 1000 kg has an engine which produces a
constant power of 50 kW. If the resistance to motion,
assumed constant is 1000 N. The maximum speed at which
the bus can travel on level road and the acceleration when
it is travelling at 25 m/s, will respectively be -
(a) 50 m/s, 1.0 m/s
2
(b) 1.0 m/s, 50 m/s
2
(c) 5.0 m/s, 10 m/s
2
(d) 10 m/s, 5m/s
2
Q.13 The power output of a 
92
U
235
 reactor if it takes 30 days to
use up 2 kg of fuel and if each fission gives 185 MeV of
energy (Avogadro number = 6 × 10
23
/mole) will be -
(a) 58.4 MW (b) 5.84 MW
(c) 584 W (d) 5840 MW
Q.14 The stopping distance for a vehicle of mass M moving with
a speed v along a level road, will be -
(µ is the coefficient of friction between tyres and the road)
(a)
2
v
g m
(b)
2
2v
g m
(c)
2
v
2g m
(d)
v
g m
Q.15The earth circles the sun once a year. How much work
would have to be done on the earth to bring it to rest
relative to the sun, (ignore the rotation of earth about -
its own axis) Given that mass of the earth is 6 × 10
24
 kg
and distance between the sun and earth is 1.5 × 10
8
 km-
(a) 2.7 × 10
33
(b) 2.7 × 10
24
(c) 1.9 × 10
23
(d) 1.9 × 10
24
Q.16A particle of mass m is moving in a horizontal circle of
radius r, under a centripetal force equal to (–k/r
2
), where k
is a constant. The total energy of the particle is -
(a) k/2r (b) – k/2r
(c ) kr (d) –k/r
Q.17 The work done by a person in carrying a box of mass 10 kg
through a vertical height of 10 m is 4900 J. The mass of
the person is -
(a) 60 kg (b) 50 kg
(c) 40 kg (d) 130 kg
Q.18A uniform rod of length 4 m and mass 20 kg is lying
horizontal on the ground. The work done in keeping it
vertical with one of its ends touching the ground, will be -
(a) 784 J (b) 392 J (c) 196 J (d) 98 J
Q.19 If g is the acceleration due to gravity on the earth’s surface,
the gain in the potential energy of an object of mass m
raised from surface of the earth to a height equal to radius
R of the earth is - [M = mass of earth]
(a)
GMm
2R
(b)
GM
R
(c)
GMm
R
(d)
GM
2R
Page 3


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A body is acted upon by a force 
ˆ ˆˆ
F i 2j 3k =-++
r
. The work
done by the force in displacing it from (0,0,0) to (0,0,4m) will
be -
(a) 12 J (b) 10 J
(c) 8 J (d) 6 J
Q.2 The work done in pulling a body of mass 5 kg along an inclined
plane (angle 60º) with coefficient of friction 0.2 through 2
m, will be -
(a) 98.08 J (b) 94.08 J
(c) 90.08 J (d) 91.08 J
Q.3 A force F
r
 = (7 – 2x + 3x
2
) N is applied on a 2 kg mass
which displaces it from x = 0 to x = 5 m. Work done in
joule is -
(a) 70 (b) 270 (c) 35 (d) 135
Q.4 An automobile of mass m accelerates from rest. If the engine
supplies a constant power P , the velocity at time t is given by -
(a) v = 
Pt
m
(b) v = 
2Pt
m
(c)
Pt
m
(d)
2Pt
m
Q.5 In the above question, the position (s) at time (t) is given by -
(a)
2Pt
t
m
æö
ç÷
èø
(b)
1/2
8P
9m
æö
ç÷
èø
t 
3/2
(c)
1/2
9P
8m
æö
ç÷
èø
t
1/2
(d)
1/2
8P
t
9m
æö
ç÷
èø
2
DPP/ P 12
Q.6 A particle moving in a straight line is acted by a force, which
works at a constant rate and changes its velocity from u to
v in passing over a distance x. The time taken will be -
(a) x = 
22
vu
vu
-
+
(b) x 
22
vu
vu
æö +
ç÷
èø
+
(c)
3
2
 (x) 
22
33
vu
vu
æö
-
ç÷
- èø
(d) x 
v
u
æö
ç÷
èø
Q.7 A chain of linear density 3 kg /m and length 8 m is lying on
the table with 4 m of chain hanging from the edge. The
work done in lifting the chain on the table will be -
(a) 117.6 J (b) 235.2 J (c) 98 J (d) 196 J
Q.8 The work done in lifting water from a well of depth 6 m
using a bucket of mass 0.5 kg and volume 2 litre, will be-
(a) 73.5 J (b) 147 J (c) 117. 6 J (d) 98 J
Q.9 An object of mass 5 kg falls from rest through a vertical
distance of 20 m and reaches a velocity of 10 m/s. How
much work is done by the push of the air on the object ?
(g = 10 m/s
2
).
(a) 350 J (b) 750 J (c) 200 J (d) 300 J
Q.10 A boy pulls a 5 kg block 20 metres along a horizontal sur-
face at a constant speed with a force directed 45° above
the horizontal. If the coefficient of kinetic friction is 0.20,
how much work does the boy do on the block?
(a) 163.32 J (b) 11.55 J
(c) 150 J (d) 115 J
Q.11 A uniform chain is held on a frictionless table with one-
fifth of its length hanging over the edge. If the chain has a
length l and a mass m, how much work is required to pull
the hanging part back on the table ?
(a) mg l / 10 (b) mg l / 5
(c) mg l / 50 (d) mg l / 2
Q.12 A bus of mass 1000 kg has an engine which produces a
constant power of 50 kW. If the resistance to motion,
assumed constant is 1000 N. The maximum speed at which
the bus can travel on level road and the acceleration when
it is travelling at 25 m/s, will respectively be -
(a) 50 m/s, 1.0 m/s
2
(b) 1.0 m/s, 50 m/s
2
(c) 5.0 m/s, 10 m/s
2
(d) 10 m/s, 5m/s
2
Q.13 The power output of a 
92
U
235
 reactor if it takes 30 days to
use up 2 kg of fuel and if each fission gives 185 MeV of
energy (Avogadro number = 6 × 10
23
/mole) will be -
(a) 58.4 MW (b) 5.84 MW
(c) 584 W (d) 5840 MW
Q.14 The stopping distance for a vehicle of mass M moving with
a speed v along a level road, will be -
(µ is the coefficient of friction between tyres and the road)
(a)
2
v
g m
(b)
2
2v
g m
(c)
2
v
2g m
(d)
v
g m
Q.15The earth circles the sun once a year. How much work
would have to be done on the earth to bring it to rest
relative to the sun, (ignore the rotation of earth about -
its own axis) Given that mass of the earth is 6 × 10
24
 kg
and distance between the sun and earth is 1.5 × 10
8
 km-
(a) 2.7 × 10
33
(b) 2.7 × 10
24
(c) 1.9 × 10
23
(d) 1.9 × 10
24
Q.16A particle of mass m is moving in a horizontal circle of
radius r, under a centripetal force equal to (–k/r
2
), where k
is a constant. The total energy of the particle is -
(a) k/2r (b) – k/2r
(c ) kr (d) –k/r
Q.17 The work done by a person in carrying a box of mass 10 kg
through a vertical height of 10 m is 4900 J. The mass of
the person is -
(a) 60 kg (b) 50 kg
(c) 40 kg (d) 130 kg
Q.18A uniform rod of length 4 m and mass 20 kg is lying
horizontal on the ground. The work done in keeping it
vertical with one of its ends touching the ground, will be -
(a) 784 J (b) 392 J (c) 196 J (d) 98 J
Q.19 If g is the acceleration due to gravity on the earth’s surface,
the gain in the potential energy of an object of mass m
raised from surface of the earth to a height equal to radius
R of the earth is - [M = mass of earth]
(a)
GMm
2R
(b)
GM
R
(c)
GMm
R
(d)
GM
2R
DPP/ P 12
3
Q.20 The potential energy between two atoms in a molecule is given
by , U
(x)
 = 
126
ab
xx
-
, where a and b are positive constant and x
is the distance between the atoms. The atoms is an stable
equilibrium, when-
(a) x = 0 (b) x = 
1/6
a
2b
æö
ç÷
èø
(c) x = 
1/6
2a
b
æö
ç÷
èø
(d) x = 
1/6
11a
5b
æö
ç÷
èø
DIRECTIONS (Q.21-Q.22) : In the following questions,
more than one of the answers  given are correct. Select the
correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct
(b) 1 and 2 are correct
(c) 2 and 4 are correct
(d) 1 and 3 are correct
Q.21A man pushes a wall and fails to displace it. Choose
incorrect statements related to his work
(1) Negative work
(2) Positive but not maximum work
(3) Maximum work
(4) No work at all
Q.22Choose the correct options –
(1) The work done by forces may be equal to change in
kinetic energy
(2) The work done by forces may be equal to change in
potential energy
(3) The work done by forces may be equal to change in
total energy
(4) The work done by forces must be equal to change in
potential energy.
DIRECTIONS (Q.23-Q.25) : Read the passage given below
and answer the questions that follows :
In the figure shown, the system is released from rest with both
the springs in unstretched positions. Mass of each block is 1 kg
and force constant of each spring is 10 N/m.
Q.23 Extension of horizontal spring in equilibrium is:
(a) 0.2 m (b) 0.4 m
(c) 0.6 m (d) 0.8 m
Q.24 Extension of vertical spring in equilibrium is
(a) 0.4 m (b) 0.2 m
(c) 0.6 m (d) 0.8 m
Q.25 Maximum speed of the block placed horizontally is:
(a) 3.21 m/s (b) 2.21 m/s
(c) 1.93 m/s (d) 1.26 m/s
DIRECTIONS (Qs. 26-Q.28) : Each of these questions contains
two statements: Statement-1 (Assertion) and Statement-2
(Reason). Each of these questions has four alternative choices,
only one of which is the correct answer. You have to select the
correct choice.
(a) Statement-1 is True, Statement-2 is True; Statement-2 is a
correct explanation for  Statement-1.
(b) Statement-1 is True, Statement-2 is True; Statement-2 is
NOT a correct explanation for Statement-1.
(c) Statement -1 is False, Statement-2 is True.
(d) Statement -1 is True, Statement-2 is False.
Page 4


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 A body is acted upon by a force 
ˆ ˆˆ
F i 2j 3k =-++
r
. The work
done by the force in displacing it from (0,0,0) to (0,0,4m) will
be -
(a) 12 J (b) 10 J
(c) 8 J (d) 6 J
Q.2 The work done in pulling a body of mass 5 kg along an inclined
plane (angle 60º) with coefficient of friction 0.2 through 2
m, will be -
(a) 98.08 J (b) 94.08 J
(c) 90.08 J (d) 91.08 J
Q.3 A force F
r
 = (7 – 2x + 3x
2
) N is applied on a 2 kg mass
which displaces it from x = 0 to x = 5 m. Work done in
joule is -
(a) 70 (b) 270 (c) 35 (d) 135
Q.4 An automobile of mass m accelerates from rest. If the engine
supplies a constant power P , the velocity at time t is given by -
(a) v = 
Pt
m
(b) v = 
2Pt
m
(c)
Pt
m
(d)
2Pt
m
Q.5 In the above question, the position (s) at time (t) is given by -
(a)
2Pt
t
m
æö
ç÷
èø
(b)
1/2
8P
9m
æö
ç÷
èø
t 
3/2
(c)
1/2
9P
8m
æö
ç÷
èø
t
1/2
(d)
1/2
8P
t
9m
æö
ç÷
èø
2
DPP/ P 12
Q.6 A particle moving in a straight line is acted by a force, which
works at a constant rate and changes its velocity from u to
v in passing over a distance x. The time taken will be -
(a) x = 
22
vu
vu
-
+
(b) x 
22
vu
vu
æö +
ç÷
èø
+
(c)
3
2
 (x) 
22
33
vu
vu
æö
-
ç÷
- èø
(d) x 
v
u
æö
ç÷
èø
Q.7 A chain of linear density 3 kg /m and length 8 m is lying on
the table with 4 m of chain hanging from the edge. The
work done in lifting the chain on the table will be -
(a) 117.6 J (b) 235.2 J (c) 98 J (d) 196 J
Q.8 The work done in lifting water from a well of depth 6 m
using a bucket of mass 0.5 kg and volume 2 litre, will be-
(a) 73.5 J (b) 147 J (c) 117. 6 J (d) 98 J
Q.9 An object of mass 5 kg falls from rest through a vertical
distance of 20 m and reaches a velocity of 10 m/s. How
much work is done by the push of the air on the object ?
(g = 10 m/s
2
).
(a) 350 J (b) 750 J (c) 200 J (d) 300 J
Q.10 A boy pulls a 5 kg block 20 metres along a horizontal sur-
face at a constant speed with a force directed 45° above
the horizontal. If the coefficient of kinetic friction is 0.20,
how much work does the boy do on the block?
(a) 163.32 J (b) 11.55 J
(c) 150 J (d) 115 J
Q.11 A uniform chain is held on a frictionless table with one-
fifth of its length hanging over the edge. If the chain has a
length l and a mass m, how much work is required to pull
the hanging part back on the table ?
(a) mg l / 10 (b) mg l / 5
(c) mg l / 50 (d) mg l / 2
Q.12 A bus of mass 1000 kg has an engine which produces a
constant power of 50 kW. If the resistance to motion,
assumed constant is 1000 N. The maximum speed at which
the bus can travel on level road and the acceleration when
it is travelling at 25 m/s, will respectively be -
(a) 50 m/s, 1.0 m/s
2
(b) 1.0 m/s, 50 m/s
2
(c) 5.0 m/s, 10 m/s
2
(d) 10 m/s, 5m/s
2
Q.13 The power output of a 
92
U
235
 reactor if it takes 30 days to
use up 2 kg of fuel and if each fission gives 185 MeV of
energy (Avogadro number = 6 × 10
23
/mole) will be -
(a) 58.4 MW (b) 5.84 MW
(c) 584 W (d) 5840 MW
Q.14 The stopping distance for a vehicle of mass M moving with
a speed v along a level road, will be -
(µ is the coefficient of friction between tyres and the road)
(a)
2
v
g m
(b)
2
2v
g m
(c)
2
v
2g m
(d)
v
g m
Q.15The earth circles the sun once a year. How much work
would have to be done on the earth to bring it to rest
relative to the sun, (ignore the rotation of earth about -
its own axis) Given that mass of the earth is 6 × 10
24
 kg
and distance between the sun and earth is 1.5 × 10
8
 km-
(a) 2.7 × 10
33
(b) 2.7 × 10
24
(c) 1.9 × 10
23
(d) 1.9 × 10
24
Q.16A particle of mass m is moving in a horizontal circle of
radius r, under a centripetal force equal to (–k/r
2
), where k
is a constant. The total energy of the particle is -
(a) k/2r (b) – k/2r
(c ) kr (d) –k/r
Q.17 The work done by a person in carrying a box of mass 10 kg
through a vertical height of 10 m is 4900 J. The mass of
the person is -
(a) 60 kg (b) 50 kg
(c) 40 kg (d) 130 kg
Q.18A uniform rod of length 4 m and mass 20 kg is lying
horizontal on the ground. The work done in keeping it
vertical with one of its ends touching the ground, will be -
(a) 784 J (b) 392 J (c) 196 J (d) 98 J
Q.19 If g is the acceleration due to gravity on the earth’s surface,
the gain in the potential energy of an object of mass m
raised from surface of the earth to a height equal to radius
R of the earth is - [M = mass of earth]
(a)
GMm
2R
(b)
GM
R
(c)
GMm
R
(d)
GM
2R
DPP/ P 12
3
Q.20 The potential energy between two atoms in a molecule is given
by , U
(x)
 = 
126
ab
xx
-
, where a and b are positive constant and x
is the distance between the atoms. The atoms is an stable
equilibrium, when-
(a) x = 0 (b) x = 
1/6
a
2b
æö
ç÷
èø
(c) x = 
1/6
2a
b
æö
ç÷
èø
(d) x = 
1/6
11a
5b
æö
ç÷
èø
DIRECTIONS (Q.21-Q.22) : In the following questions,
more than one of the answers  given are correct. Select the
correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct
(b) 1 and 2 are correct
(c) 2 and 4 are correct
(d) 1 and 3 are correct
Q.21A man pushes a wall and fails to displace it. Choose
incorrect statements related to his work
(1) Negative work
(2) Positive but not maximum work
(3) Maximum work
(4) No work at all
Q.22Choose the correct options –
(1) The work done by forces may be equal to change in
kinetic energy
(2) The work done by forces may be equal to change in
potential energy
(3) The work done by forces may be equal to change in
total energy
(4) The work done by forces must be equal to change in
potential energy.
DIRECTIONS (Q.23-Q.25) : Read the passage given below
and answer the questions that follows :
In the figure shown, the system is released from rest with both
the springs in unstretched positions. Mass of each block is 1 kg
and force constant of each spring is 10 N/m.
Q.23 Extension of horizontal spring in equilibrium is:
(a) 0.2 m (b) 0.4 m
(c) 0.6 m (d) 0.8 m
Q.24 Extension of vertical spring in equilibrium is
(a) 0.4 m (b) 0.2 m
(c) 0.6 m (d) 0.8 m
Q.25 Maximum speed of the block placed horizontally is:
(a) 3.21 m/s (b) 2.21 m/s
(c) 1.93 m/s (d) 1.26 m/s
DIRECTIONS (Qs. 26-Q.28) : Each of these questions contains
two statements: Statement-1 (Assertion) and Statement-2
(Reason). Each of these questions has four alternative choices,
only one of which is the correct answer. You have to select the
correct choice.
(a) Statement-1 is True, Statement-2 is True; Statement-2 is a
correct explanation for  Statement-1.
(b) Statement-1 is True, Statement-2 is True; Statement-2 is
NOT a correct explanation for Statement-1.
(c) Statement -1 is False, Statement-2 is True.
(d) Statement -1 is True, Statement-2 is False.
4
DPP/ P 12
Q.26 As shown in the figure, a uniform sphere is rolling on a
horizontal surface without slipping, under the action of a
horizontal force F.
F
Statement - 1 : Power  developed due to friction force is
zero.
Statement - 2 : Power developed by gravity force is non-
zero.
Q.27 Statement - 1 : Sum of work done by the Newton’s 3
rd
 law
pair internal forces, acting between two particles may be
zero.
Statement - 2 : If two particles undergo same displacement
then work done by Newton’s 3
rd 
law pair forces on them is
of opposite sign and equal magnitude.
Q.28 Statement - 1: A particle moves along a straight line with
constant velocity . Now a constant non-zero force is applied
on the particle in direction opposite to its initial velocity.
After the force is applied, the net work done by this force
may be zero in certain time intervals.
Statement - 2 : The work done by a force acting on a particle
is zero in any time interval if the force is always
perpendicular to velocity of the particle.