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Work Power and Energy

505 Questions Start Allen Test
All Exams Allen Objective Errorless
Q476 Objective Taking it together MCQ
A body of mass 0.5 kg travels in a straight line with velocity $v = a x^{3/2}$ , where $a = 5 m^{-1/2} s^{-1}$ . The work done by the net force during its displacement from x = 0 to x = 2 m is [NCERT Exemplar]
A.
1.5 J
B.
50 J
C.
10 J
D.
100 J
Q477 Objective Taking it together MCQ
The figure shows a particle sliding on a frictionless track, which terminates in a straight horizontal section. If the particle starts slipping from the point A, how far away from the track will the particle hit the ground?
A.
1m
B.
2m
C.
3m
D.
4m
Q478 Objective Taking it together MCQ
A uniform chain has a mass M and length L. It is placed on a frictionless table with length $l_{0}$ hanging over the edge. The chain begins to slide down. Then, the speed v with which the end slides down from the edge is given by
A.
$v = \sqrt{\frac{g}{L}(L + l_{0})}$
B.
$v = \sqrt{\frac{g}{L}(L - l_{0})}$
C.
$v = \sqrt{\frac{g}{L}(L^{2} - l_{0}^{2})}$
D.
$v = \sqrt{2g(L - l_{0})}$
Q479 Objective Taking it together MCQ
A bead of mass 1/2 kg starts from rest from A to B move in a vertical plane along a smooth fixed quarter ring of radius 5 m, under the action of a constant horizontal force F = 5 N as shown in figure. The speed of bead as it reaches the point B is (Take, $g = 10 \, ms^{-2}$ )
A.
$14.14\mathrm{ms}^{-1}$
B.
$7.07\mathrm{ms}^{-1}$
C.
$5\mathrm{ms}^{-1}$
D.
$25\mathrm{ms}^{-1}$
Q480 Objective Taking it together MCQ
A car of mass m is accelerating on a level smooth road under the action of a single force F. The power delivered to the car is constant and equal to P. If the velocity of the car at an instant is v, then after travelling how much distance will it become double?
A.
$\frac{7mv^3}{3P}$
B.
$\frac{4mv^3}{3P}$
C.
$\frac{mv^3}{P}$
D.
$\frac{18mv^3}{7P}$
Q481 Objective Taking it together MCQ
A particle is released from a height $H$ . At certain height, its kinetic energy is two times its potential energy. Height and speed of particle at that instant are
A.
$\frac{H}{3}, \sqrt{\frac{2gH}{3}}$
B.
$\frac{H}{3}, 2\sqrt{\frac{gH}{3}}$
C.
$\frac{2H}{3}, \sqrt{\frac{2gH}{3}}$
D.
$\frac{H}{3}, \sqrt{2gH}$
Q482 Objective Taking it together MCQ
A force of $F = 0.5 \, \text{N}$ is applied on lower block as shown in figure . The work done by lower block on upper block for a displacement of $3 \, \text{m}$ of the upper block with respect to ground is (Take, $g = 10 \, \text{ms}^{-2}$ )
A.
$-0.5\mathrm{J}$
B.
$0.5\mathrm{J}$
C.
$2\mathrm{J}$
D.
$-2\mathrm{J}$
Q483 Objective Taking it together MCQ
A body is moving unidirectionally under the influence of a source of constant power supplying energy. Which of the following diagrams shown in figure correctly represents the displacement-time curve for its motion? [NCERT Exemplar]
A.
B.
C.
D.
Q484 Objective Taking it together MCQ
A small block of mass m is kept on a rough inclined surface of inclination $\theta$ fixed in an elevator. The elevator goes up with a uniform velocity v and the block does not slide on the wedge. The work done by the force of friction on the block in a time t will be
A.
zero
B.
$mgvt \cos^{2} \theta$
C.
$mgvt \sin^{2} \theta$
D.
$\frac{1}{2} mgvt \sin 2\theta$
Q485 Objective Taking it together MCQ
A pendulum of mass 1 kg and length l = 1m is released from rest at angle $\theta = 60^{\circ}$ . The power delivered by all the forces acting on the bob at angle $\theta = 30^{\circ}$ will be (Take, $g = 10 \, ms^{-2}$ )
A.
13.5 W
B.
20.4 W
C.
24.6 W
D.
zero
Q486 Objective Taking it together MCQ
A uniform flexible chain of mass m and length l hangs in equilibrium over a smooth horizontal pin of negligible diameter. One end of the chain is given a small vertical displacement, so that the chain slips over the pin. The speed of chain when it leaves pin is
A.
$\sqrt{\frac{gl}{2}}$
B.
$\sqrt{gl}$
C.
$\sqrt{2gl}$
D.
$\sqrt{3gl}$
Q487 Objective Taking it together MCQ
The potential energy of a particle of mass 1 kg is $U = 10 + (x - 2)^{2}$ . Here, U is in joule and x in metre on the positive X-axis. Particle travels up to $x = +6 \, m$ . Choose the correct option.
A.
On negative $X$ -axis, particle travels up to $x = -2\mathrm{m}$
B.
The maximum kinetic energy of the particle is 16 J
C.
Both a) and b) are correct
D.
Both a) and b) are incorrect
Q488 Objective Taking it together MCQ
A plank of mass 10 kg and a block of mass 2 kg are placed on a horizontal plane as shown in the figure. There is no friction between plane and plank. The coefficient of friction between block and plank is 0.5. A force of 60 N is applied on plank horizontally. In first 2 s, the work done by friction on the block is
A.
āˆ’100 J
B.
100 J
C.
zero
D.
200 j
Q489 Objective Taking it together MCQ
A block of mass m is pulled along a horizontal surface by applying a force at an angle $\theta$ with the horizontal. If the block travels with a uniform velocity and has a displacement d and the coefficient of friction is $\mu$ , then the work done by the applied force is
A.
$\frac{\mu mgd}{\cos\theta + \mu \sin\theta}$
B.
$\frac{\mu mgd\cos\theta}{\cos\theta + \mu\sin\theta}$
C.
$\frac{\mu mgd \sin\theta}{\cos\theta + \mu \sin\theta}$
D.
$\frac{\mu mgd\cos\theta}{\cos\theta - \mu\sin\theta}$
Q490 Objective Taking it together MCQ
An ideal massless spring S can be compressed 1 m by a force of 100 N in equilibrium. The same spring is placed at the bottom of a frictionless inclined plane inclined at $30^{\circ}$ to the horizontal. A 10 kg block M is released from rest at the top of the incline and is brought to rest momentarily after compressing the spring by 2 m. If $g = 10 \, ms^{-2}$ , what is the speed of mass just before it touches the spring? image.png
A.
$\sqrt{20}\ \mathrm{m\,s^{-1}}$
B.
$\sqrt{30}\ \mathrm{m\,s^{-1}}$
C.
$\sqrt{10}\ \mathrm{m\,s^{-1}}$
D.
$\sqrt{40}\ \mathrm{m\,s^{-1}}$
Q491 Objective Assertion and Reason MCQ
Assertion At stable equilibrium position of a body, kinetic energy cannot be zero. Because it is maximum. Reason During oscillations of a body, potential energy is minimum at stable equilibrium position.
A.
If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
B.
If both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
C.
If Assertion is correct but Reason is incorrect.
D.
If Assertion is incorrect but Reason is correct.
Q492 Objective Assertion and Reason MCQ
Assertion If work done by conservative force is negative, then potential energy associated with that force should increase. Reason This is according to the relation, $\Delta U = -W$ . Here, $\Delta U$ is change in potential energy and W is work done by conservative force.
A.
If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
B.
If both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
C.
If Assertion is correct but Reason is incorrect.
D.
If Assertion is incorrect but Reason is correct.
Q493 Objective Assertion and Reason MCQ
Assertion If the surface between the blocks A and B is rough, then work done by friction on block B is always negative. Reason Total work done by friction in both the blocks is always zero.
A.
If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
B.
If both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
C.
If Assertion is correct but Reason is incorrect.
D.
If Assertion is incorrect but Reason is correct.
Q494 Objective Assertion and Reason MCQ
Assertion Force applied on a block moving in one dimension is producing a constant power, then the motion should be uniformly accelerated. Reason This constant power multiplied with time is equal to the change in kinetic energy.
A.
If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
B.
If both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
C.
If Assertion is correct but Reason is incorrect.
D.
If Assertion is incorrect but Reason is correct.
Q495 Objective Assertion and Reason MCQ
Assertion Total work done by spring may be positive, negative or zero. Reason Direction of spring force is always towards mean position.
A.
If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
B.
If both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
C.
If Assertion is correct but Reason is incorrect.
D.
If Assertion is incorrect but Reason is correct.
Q496 Objective Assertion and Reason MCQ
Assertion At any instant, the magnitude of rate of change of potential energy of the projectile of mass 1 kg is numerically equal to magnitude of $a \cdot v$ (where, a is acceleration due to gravity and v is velocity at that instant) Reason The graph representing power delivered by the gravitational force acting on the projectile with time will be straight line with negative slope.
A.
If both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
B.
If both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
C.
If Assertion is correct but Reason is incorrect.
D.
If Assertion is incorrect but Reason is correct.
Q497 Objective Statement based questions MCQ
Mark out the correct statement(s).
A.
Total work done by internal forces on a system is always zero.
B.
Total work done by internal forces on a system may sometimes be zero.
C.
Total work done by friction can never be zero.
D.
Total work done by friction is always zero.
Q498 Objective Statement based questions MCQ
Two inclined frictionless tracks, one gradual and the other steep meet at A from where two stones are allowed to slide down from rest, one on each track as shown in figure. [NCERT Exemplar] Which of the following statement(s) is/are correct?
A.
Both the stones reach the bottom at the same time but not with the same speed.
B.
Both the stones reach the bottom with the same speed and stone I reaches the bottom earlier than stone II.
C.
Both the stones reach the bottom with the same speed and stone II reaches the bottom earlier than stone I.
D.
Both the stones reach the bottom at different times and with different speeds.
Q499 Objective Statement based questions MCQ
In position A, kinetic energy of a particle is 60 J and potential energy is -20 J. In position B, kinetic energy is 100 J and potential energy is 40 J. Choose the correct statement, if the particle moves from A to B.
A.
Work done by conservative forces is 50 J.
B.
Work done by external forces is 40 J.
C.
Net work done by all the forces is 40 J.
D.
Net work done by all the forces is 100 J.
Q500 Objective Statement based questions MCQ
Which of the following statement(s) is/are correct? I. Spring force is a conservative force. II. Potential energy is defined only for conservative forces.
A.
Only I
B.
Only II
C.
Both I and II
D.
Neither I nor II