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Work Power and Energy

505 Questions Start Allen Test
All Exams Allen Objective Errorless
Q401 Allen (Analytical Questions) MCQ
In the below image If both blocks A and B are moving together, then select correct statements -
(a) Work done by the friction on block ā€˜Aā€™ is zero
(b) Work done by the friction on block ā€˜Aā€™ is positive
(c) Work done by the friction on block ā€˜Bā€™ is negative
(d) Work done by friction forces on system (A) and (B) are zero
A.
a, c and d
B.
b, c and d
C.
a and d
D.
none of these
Q402 Allen (Analytical Questions) MCQ
For a system of particles - (a) The work done by all external forces is equal to change in kinetic energy (b) The work done by all forces is equal to change in mechanical energy Select the correct statements :
A.
only a
B.
only b
C.
both a and b
D.
none of these
Q403 Allen (Analytical Questions) MCQ
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason
(R).
Assertion (A) : Kinetic energy of a system can be increased without applying external force on the system.
Reason (R) : If external forces are absent then work done by internal forces is equal to change in kinetic energy.
In the light of the above statements,
choose the most appropriate answer from the options given below:
A.
Both (A) and (R) are true and (R) is the correct explanation of (A).
B.
Both (A) and (R) are true and (R) is NOT the correct explanation of (A).
C.
(A) is true but (R) is false.
D.
(A) is false but (R) is true.
Q404 Allen (Analytical Questions) MCQ
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Work done is positive when force acts in the direction of displacement.
Reason (R) : Work done by frictional force cannot be positive.
In the light of the above statements,
choose the most appropriate answer from the options given below:
A.
Both (A) and (R) are true and (R) is the correct explanation of (A).
B.
Both (A) and (R) are true and (R) is NOT the correct explanation of (A).
C.
(A) is true but (R) is false.
D.
(A) is false but (R) is true.
Q405 Allen (Analytical Questions) Match the Columns
Assume that in space potential energy U-depends on x-coordinate only by :
$\mathrm{U} = (\mathrm{x} - 3) ^ {2} (2 - \mathrm{x})$

A mass m can be kept on x-axis. In each position indicated in Column-I, comment on the situation from Column-II.
Column-IColumn-II
(A)$x = \frac{7}{3}$
(B)$x = 2$
(C)$x = 3$
(P)Stable equilibrium
(Q)Unstable equilibrium
(R)Neutral equilibrium
(S)Not in equilibrium
A.
A ā†’ P, B ā†’ S, C ā†’ R
B.
A ā†’ S, B ā†’ P, C ā†’ Q
C.
A ā†’ P, B ā†’ S, C ā†’ Q
D.
A ā†’ Q, B ā†’ S, C ā†’ P
Q406 Allen (Analytical Questions) MCQ
The potential energy (in joules) function of a particle in a region of space is given as : $\mathrm{U} = (2 \mathrm{x} ^ {2} + 3 \mathrm{y} ^ {3} + 2 \mathrm{z})$ Here x, y and z are in metres. Find the magnitude of x component of force (in newton) acting on the particle at point P (1m, 2m, 3m).
A.
4
B.
2
C.
6
D.
None
Q407 Errorless Conservation of Energy and Momentum MCQ
A wire, which passes through the hole is a small bead, is bent in the form of quarter of a circle. The wire is fixed vertically on ground as shown in the figure. The bead is released from near the top of the wire and it slides along the wire without friction. As the bead
A.
Always radially outwards
B.
Always radially inwards
C.
Radially outwards initially and radially inwards later
D.
Radially inwards initially and radially outwards later
Q408 Errorless POWER MCQ
A body of mass M is moving with a uniform speed of 10m/s on frictionless surface under the influence of two forces $F_{1}$ and $F_{2}$ . The net power of the system is image.png
A.
$10F_{1}F_{2}M$
B.
$10(F_{1}+F_{2})M$
C.
$(F_{1}+F_{2})M$
D.
Zero
Q409 Errorless Elastic and Inelastic Collision MCQ
A ball is thrown vertically downwards from a height of 20 m with an initial velocity $v_{0}$ . It collides with the ground loses 50 percent of its energy in collision and rebounds to the same height. The initial velocity $v_{0}$ is (Take $g = 10 ms^{-2}$ )
A.
$20 ms^{-1}$
B.
$28 ms^{-1}$
C.
$10 ms^{-1}$
D.
$14 ms^{-1}$
Q410 Errorless Critical Thinking MCQ
Two particles of equal mass m have respective initial velocities $u\hat{i}$ and $u\left(\frac{\hat{i}+\hat{j}}{2}\right)$ . They collide completely inelastically. The energy lost in the process is
A.
$3/4mu^{2}$
B.
$1/8mu^{2}$
C.
$\sqrt{\frac{2}{3}}mu^{2}$
D.
$\frac{1}{3}mu^{2}$
Q411 Errorless Assertion and Reason MCQ
Assertion : If two protons are brought near one another, the potential energy of the system will increase. Reason : The charge on the proton is $+1.6 \times 10^{-19} C$ .
A.
If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.
If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.
If assertion is true but reason is false.
D.
If the assertion and reason both are false.
E.
If assertion is false but reason is true.
Q412 Errorless Assertion and Reason MCQ
Assertion : Mass and energy are not conserved separately, but are conserved as a single entity called mass-energy. Reason : Mass and energy conservation can be obtained by Einstein equation for energy.
A.
If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.
If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.
If assertion is true but reason is false.
D.
If the assertion and reason both are false.
E.
If assertion is false but reason is true.
Q413 Errorless Assertion and Reason MCQ
Assertion : Work done by friction on a body sliding down an inclined plane is positive. Reason : Work done is greater than zero, if angle between force and displacement is acute or both are in same direction.
A.
If both assertion and reason are true and the reason is the correct explanation of the assertion.
B.
If both assertion and reason are true but reason is not the correct explanation of the assertion.
C.
If assertion is true but reason is false.
D.
If the assertion and reason both are false.
E.
If assertion is false but reason is true.
Q414 Errorless Self Evaluation Test MCQ
A horizontal force of 5 N is required to maintain a velocity of 2 m/s for a block of 10 kg mass sliding over a rough surface. The work done by this force in one minute is
A.
600 J
B.
60 J
C.
6 J
D.
6000 J
Q415 Errorless Self Evaluation Test MCQ
Work done in time $t$ on a body of mass $m$ which is accelerated from rest to a speed $v$ in time $t_1$ as a function of time $t$ is given by
A.
$\frac{1}{2}m\frac{v}{t_1}t^2$
B.
$m\frac{v}{t_1}t^2$
C.
$\frac{1}{2}\left(\frac{mv}{t_1}\right)^2t^2$
D.
$\frac{1}{2}m\frac{v^2}{t_1^2}t^2$
Q416 Errorless Self Evaluation Test MCQ
When a body moves with some friction on a surface
A.
It loses kinetic energy but momentum is constant
B.
It loses kinetic energy but gains potential energy
C.
Kinetic energy and momentum both decrease
D.
Mechanical energy is conserved
Q417 Errorless Self Evaluation Test MCQ
A bullet of mass m moving with velocity v strikes a suspended wooden block of mass M. If the block rises to a height h, the initial velocity of the block will be
A.
$\sqrt{2gh}$
B.
$\frac{M+m}{m}\sqrt{2gh}$
C.
$\frac{m}{M+m}2gh$
D.
$\frac{M+m}{M}\sqrt{2gh}$
Q418 Errorless Self Evaluation Test MCQ
The slope of kinetic energy displacement curve of a particle in motion is
A.
Equal to the acceleration of the particle
B.
Inversely proportional to the acceleration
C.
Directly proportional to the acceleration
D.
None of the above
Q419 Errorless Self Evaluation Test MCQ
The energy required to accelerate a car from 10 m/s to 20 m/s is how many times the energy required to accelerate the car from rest to 10 m/s
A.
Equal
B.
4 times
C.
2 times
D.
3 times
Q420 Errorless Self Evaluation Test MCQ
A body of mass 2 kg slides down a curved track which is quadrant of a circle of radius 1 metre. All the surfaces are frictionless. If the body starts from rest, its speed at the bottom of the track is
A.
4.43 m/sec
B.
2 m/sec
C.
0.5 m/sec
D.
19.6 m/sec
Q421 Errorless Self Evaluation Test MCQ
A bomb of mass 3m kg explodes into two pieces of mass m kg and 2m kg. If the velocity of m kg mass is 16 m/s, the total kinetic energy released in the explosion is
A.
192 mJ
B.
96 mJ
C.
384 mJ
D.
768 mJ
Q422 Errorless Self Evaluation Test MCQ
Identify the false statement from the following
A.
Work-energy theorem is not independent of Newton's second law.
B.
Work-energy theorem holds in all inertial frames
C.
Work done by friction over a closed path is zero
D.
No potential energy can be associated with friction
E.
Work done is a scalar quantity
Q423 Objective Taking it together MCQ
A body is falling freely under the action of gravity alone in vacuum. Which of the following quantities remain constant during the fall? [NCERT Exemplar]
A.
Kinetic energy
B.
Potential energy
C.
Total mechanical energy
D.
Total linear momentum
Q424 Objective Taking it together MCQ
An electron and a proton are moving under the influence of mutual forces. In calculating the change in the kinetic energy of the system during motion, one ignores the magnetic force of one on another. This is because [NCERT Exemplar]
A.
the two magnetic forces are equal and opposite, so they produce no net effect
B.
the magnetic forces do not work on each particle
C.
the magnetic forces do equal and opposite (but non-zero) work on each particle
D.
the magnetic forces are necessarily negligible
Q425 Objective Taking it together MCQ
An engine exerts a force $\mathbf{F} = (20\hat{\mathbf{i}} - 3\hat{\mathbf{j}} + 5\hat{\mathbf{k}})$ N and moves with velocity $\mathbf{v} = (6\hat{\mathbf{i}} + 20\hat{\mathbf{j}} - 3\hat{\mathbf{k}})$ ms $^{-1}$ . The power of the engine (in watt) is
A.
45
B.
75
C.
20
D.
10