← Back to Physics-I

Work Power and Energy

505 Questions Start Allen Test
All Exams Allen Objective Errorless
Q451 Objective Taking it together MCQ
A particle moves on a rough horizontal ground with some initial velocity, say $v_{0}$ . If $\left(\frac{3}{4}\right)$ th of its kinetic energy is lost due to friction in time $t_{0}$ , then coefficient of friction between the particle and the ground is
A.
$\frac{v_{0}}{2gt_{0}}$
B.
$\frac{v_{0}}{4gt_{0}}$
C.
$\frac{3v_{0}}{4gt_{0}}$
D.
$\frac{v_{0}}{gt_{0}}$
Q452 Objective Taking it together MCQ
If a body of mass 200 g falls from a height 200 m and its total potential energy is converted into kinetic energy at the point of contact of the body with the surface, then decrease in potential energy of the body at the contact is (Take, $g = 10 \, ms^{-2}$ )
A.
900 J
B.
600 J
C.
400 J
D.
200 J
Q453 Objective Taking it together MCQ
A stone of mass 2 kg is projected upwards with kinetic energy of 98 J. The height at which the kinetic energy of the body becomes half of its original value will be (Take, $g = 9.8ms^{-2}$ )
A.
5 m
B.
2.5 m
C.
1.5 m
D.
0.5 m
Q454 Objective Taking it together MCQ
A toy gun uses a spring of very large value of force constant k. When charged before being triggered in the upward direction, the spring is compressed by a small distance x. If mass of shot is m, on being triggered, it will go up to a height of
A.
$\frac{kx^{2}}{mg}$
B.
$\frac{x^{2}}{kmg}$
C.
$\frac{kx^{2}}{2mg}$
D.
$\frac{(kx)^{2}}{mg}$
Q455 Objective Taking it together MCQ
Water falling from a 50 m high fall is to be used for generating electrical energy. If $1.8 \times 10^{5}$ kg of water falls per hour and half the gravitational potential energy can be converted into electrical energy, how many 100 W bulb can be lit?
A.
50
B.
125
C.
150
D.
200
Q456 Objective Taking it together MCQ
Given that the displacement of the body (in metre) is a function of time as follows $x = 2t^{4} + 5$ The mass of the body is 2 kg. What is the increase in its kinetic energy one second after the start of motion?
A.
8 J
B.
16 J
C.
32 J
D.
64 J
Q457 Objective Taking it together MCQ
An object of mass m is tied to a string of length L and a variable horizontal force is applied on it which starts at zero and gradually increases until the string makes an angle $\theta$ with the vertical. Work done by the force F is
A.
mgL (1 - sin $\theta$ )
B.
mgL
C.
mgL (1 - cos $\theta$ )
D.
mgL (1 + cos $\theta$ )
Q458 Objective Taking it together MCQ
A body is attached to the lower end of a vertical spiral spring and it is gradually lowered to its equilibrium position. This stretches the spring by a length d. If the same body attached to the same spring is allowed to fall suddenly, what would be the maximum stretching in this case?
A.
d
B.
2d
C.
3d
D.
(1/2)d
Q459 Objective Taking it together MCQ
Kinetic energy of a particle moving in a straight line varies with time t as $K = 4t^{2}$ . The force acting on the particle
A.
is constant
B.
is increasing
C.
is decreasing
D.
first increases and then decreases
Q460 Objective Taking it together MCQ
Three particles A, B and C are projected from the top of a tower with the same speed. A is thrown straight upwards, B straight down and C horizontally. They hit the ground with speeds $v_{A}$ , $v_{B}$ and $v_{C}$ , then which of the following is correct?
A.
$v_{A} = v_{B} > v_{C}$
B.
$v_{A} = v_{B} = v_{C}$
C.
$v_{A} > v_{B} = v_{C}$
D.
$v_{B} > v_{C} > v_{A}$
Q461 Objective Taking it together MCQ
A particle is moving in a conservative force field from point A to point B. $U_{A}$ and $U_{B}$ are the potential energies of the particle at points A and B; and $W_{C}$ is the work done by conservative forces in the process of taking the particle from A and B. Which of the following is true?
A.
$W_{C} = U_{B} - U_{A}$
B.
$W_{C} = U_{A} - U_{B}$
C.
$U_{A} > U_{B}$
D.
$U_{B} > U_{A}$
Q462 Objective Taking it together MCQ
Power supplied to a particle of mass 2 kg varies with time as $P = \frac{3t^{2}}{2}$ W. Here, t is in second. If particle is rest at t = 0, then velocity of particle at time t = 2 s will be
A.
$1 \, ms^{-1}$
B.
$4 \, ms^{-1}$
C.
$2 \, ms^{-1}$
D.
$2\sqrt{2} \, ms^{-1}$
Q463 Objective Taking it together MCQ
An open knife edge of mass m is dropped from a height h on a wooden floor. If the blade penetrates up to the depth d into the wood, the average resistance offered by the wood to the knife edge is
A.
$mg\left(1+\frac{h}{d}\right)$
B.
$mg\left(1+\frac{h}{d}\right)^{2}$
C.
$mg\left(1-\frac{h}{d}\right)$
D.
$mg\left(1+\frac{d}{h}\right)$
Q464 Objective Taking it together MCQ
If v be the instantaneous velocity of the body dropped from the top of a tower, when it is located at height h, then which of the following remains constant?
A.
$gh + v^{2}$
B.
$gh + \frac{v^{2}}{2}$
C.
$gh - \frac{v^{2}}{2}$
D.
$gh - v^{2}$
Q465 Objective Taking it together MCQ
A block of mass 1 kg slides down a rough inclined plane of inclination $60^{\circ}$ starting from its top. If coefficient of kinetic friction is 0.5 and length of the plane d = 2 m, then work done against friction is
A.
2.45 J
B.
4.9 J
C.
9.8 J
D.
19.6 J
Q466 Objective Taking it together MCQ
A raindrop falling from a height h above ground, attains a near terminal velocity when it has fallen through a height $(3/4)h$ . Which of the diagrams shown in figure correctly shows the change in kinetic and potential energy of the drop during its fall up to the ground? [NCERT Exemplar]
A.
B.
C.
D.
Q467 Objective Taking it together MCQ
In a shotput event, an athlete throws the shotput of mass 10 kg with an initial speed of $1 \, ms^{-1}$ at $45^{\circ}$ from a height 1.5 m above ground. Assuming air resistance to be negligible and acceleration due to gravity to be $10 \, ms^{-2}$ , the kinetic energy of the shotput when it just reaches the ground will be
A.
2.5 J
B.
5 J
C.
52.5 J
D.
155 J
Q468 Objective Taking it together MCQ
A block of mass m is attached to two unstretched springs of spring constants k, each as shown. The block is displaced towards right through a distance x and is released. The speed of the block as it passes through the mean position will be
A.
$x\sqrt{\frac{m}{2k}}$
B.
$x\sqrt{\frac{2k}{m}}$
C.
$x\sqrt{\frac{m}{k}}$
D.
$x\frac{2k}{m}$
Q469 Objective Taking it together MCQ
A particle of mass 1 g executes an oscillatory motion on the concave surface of a spherical dish of radius 2m placed on a horizontal plane. If the motion of the particle begins from a point on the dish at a height of 1 cm from the horizontal plane, the total distance covered by the particle before it comes to rest, is (Curved surface is smooth and $\mu = 0.01$ for horizontal surface)
A.
2 cm
B.
10 cm
C.
1 cm
D.
20 cm
Q470 Objective Taking it together MCQ
The net work done by the tension in the figure when the bigger block of mass M touches the ground is
A.
$+Mgd$
B.
$-(M + m)gd$
C.
$-mgd$
D.
zero
Q471 Objective Taking it together MCQ
A block $A$ of mass $M$ rests on a wedge $B$ of mass $2M$ and inclination $\theta$ . There is sufficient friction between $A$ and $B$ , so that $A$ does not slip on $B$ . If there is no friction between $B$ and ground, the compression in spring is
A.
$\frac{Mg\cos\theta}{k}$
B.
$\frac{Mg\cos\theta\sin\theta}{k}$
C.
$\frac{Mg\sin\theta}{k}$
D.
zero
Q472 Objective Taking it together MCQ
The force required to stretch a spring varies with the distance as shown in the figure. If the experiment is performed with the above spring of half the length, the line OA will
A.
shift towards F-axis
B.
shift towards X-axis
C.
remain as it is
D.
become double in length
Q473 Objective Taking it together MCQ
A motor drives a body along a straight line with a constant force. The power P developed by the motor must vary with time t as
A.
B.
C.
D.
Q474 Objective Taking it together MCQ
A force F acting on a body depends on its displacement s as $F \propto s^{-1/3}$ . The power delivered by F will depend on displacement as
A.
$s^{2/3}$
B.
$s^{-5/3}$
C.
$s^{1/2}$
D.
$s^{0}$
Q475 Objective Taking it together MCQ
The force acting on a body moving along X-axis varies with the position of the particle as shown in the figure. The body is in stable equilibrium at
A.
$x = x_{1}$
B.
$x = x_{2}$
C.
Both $x_{1}$ and $x_{2}$
D.
Neither $x_{1}$ nor $x_{2}$