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Class 11
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Physics
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Work, Energy and Power
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Hard Questions
Work Energy And Power
Physics
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If collision between the block and the incline is completely elastic, then the vertical (upward) component of the velocity of the block at point B, immediately after it strikes the second incline is
A
3
0
m
/
s
B
1
5
m
/
s
C
0
D
−
1
5
m
/
s
Hard
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>
The figure shows a block having a small basket in it and an small inclined plane (with fixed angle) is rigidly attached to the block. The combined mass (including incline plane) of all these is M = 5 kg. Initially they are at rest. Now identical balls each of mass m=1 kg are thrown horizontally with velocity v = 5m/s (with respect to ground) which strike the inclined plane and then are collected in the small basket. Assume that in the basket balls come to rest with respect to basket. Choose the correct statement(s) from the following :
A
After collecting 5 balls the speed of the block will be 2.5 m/s
B
After collecting 10 balls the speed of the block will be (10/3) m/s
C
The velocity of the block will never be exactly 5 m/s no matter how many balls are collected in the basket.
D
Increase in speed of the block will be same every time for collection of each ball in the basket
Hard
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>
The work done by the force
F
=
A
(
y
2
i
^
+
2
x
2
j
^
)
, where
A
is a constant and
x
&
y
are in meters around the path shown is :
A
z
e
r
o
B
A
d
C
A
d
2
D
A
d
3
Hard
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>
A ball of mass m moves towards a moving wall of infinite mass with a speed 'v' along the normal to the wall. The speed of the wall is 'u' toward the ball. The speed of the ball after elastic collision with wall is
A
u
+
v
away from the wall
B
2
u
+
v
away from the wall
C
∣
u
−
v
∣
away from the wall
D
∣
v
−
2
u
∣
away from the wall
Hard
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>
A force
F
=
(
3
t
i
^
+
5
j
^
)
N acts on a particle whose position vector varies as
S
=
(
2
t
2
i
^
+
5
j
^
)
m, where
t
is time in seconds. The work done by this force from
t
=
0
to
t
=
2
s
is:
A
23 J
B
32 J
C
zero
D
can't be obtained
Hard
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>
The force exerted by a compression device is given by
F
(
x
)
=
k
x
(
x
−
l
)
for
0
≤
x
≤
l
, where
l
is the maximum possible compression,
x
is the compression and
k
is the constant. Work done to compress the device by a distance
d
will be maximum when
A
d
=
4
l
B
d
=
2
l
C
d
=
2
l
D
d
=
l
Hard
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>
A particle of mass
m
0
,
travelling at speed
v
0
,
strikes a stationary particle of mass
2
m
0
.
As a result, the particle of mass
m
0
is deflected through
4
5
o
and has a final speed of
2
v
0
. Then the speed of the particle of mass
2
m
0
after this collision is
A
2
v
0
B
2
2
v
0
C
2
v
0
D
2
v
0
Hard
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>
A particle of mass
m
moves along the quarter section of the circular path whose centre is at the origin. The radius of the circular path is
a
. A force
F
=
y
i
^
−
x
j
^
newton acts on the particle, where
x
,
y
denote the coordinates of position of the particle. The work done by this force in taking the particle from point A (
a
,
0
) to point B (
0
,
a
) along the circular path is
A
4
π
a
2
J
B
2
π
a
2
J
C
3
π
a
2
J
D
N
o
n
e
o
f
t
h
e
s
e
Hard
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>
The balls, having linear momenta
p
1
=
p
i
^
and
p
2
=
−
p
i
^
, undergo a collision in free space. There is no extemal force acting on the balls. Let
p
1
and
p
2
be their final momenta. The following option(s) is (are) NOT ALLOWED for any non-zero value of
p
,
a
1
,
a
2
,
b
1
,
b
2
,
c
1
and
c
2
.
A
p
1
=
a
1
i
^
+
b
1
j
^
+
c
1
k
^
;
p
2
=
a
2
i
+
b
2
j
^
B
p
1
=
c
1
k
^
;
p
2
=
c
2
k
^
C
p
1
=
a
1
i
+
b
1
j
^
+
c
1
k
^
;
p
2
=
a
2
i
^
+
b
2
j
^
−
c
1
k
^
D
p
1
=
a
1
i
^
+
b
1
j
^
;
p
2
=
a
2
i
+
b
1
j
^
Hard
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>
An elastic string carrying a body of mass
m
at one end extends by
1
.
5
c
m
. If the body rotates in vertical circle with critical velocity, the extension in the string at the lowest position is:
A
3
.
0
c
m
B
4
.
5
c
m
C
1
.
5
c
m
D
9
.
0
c
m
Hard
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>