JEE Questions for Physics Work Energy And Power Quiz 2 - MCQExams.com

Two rectangular blocks A and B of masses 2 kg and 3kg respectively are connected by a spring of spring constant 10.8 Nm-1 and are placed on a frictionless horizontal surface. The block A was given an initial velocity of 0.15 ms-1 in the direction shown in the figure. The maximum compression of the spring during the motion is
Physics-Work Energy and Power-97400.png
  • 0.01 m
  • 0.02 m
  • 0.05 m
  • 0.03 m
A particle is acted upon by a force F which varies with position x as shown in figure. If the particle at x = 0 has kinetic energy of 25 J, then the kinetic energy of the particle at, x =16 m is
Physics-Work Energy and Power-97402.png
  • 45 J
  • 30 J
  • 70 J
  • 135 J
  • 20 J
A rod of mass m and length l is made to stand at an angle of 60° with the vertical. Potential energy of the rod in this position is
  • mgl
  • 2)
    Physics-Work Energy and Power-97404.png

  • Physics-Work Energy and Power-97405.png

  • Physics-Work Energy and Power-97406.png

  • Physics-Work Energy and Power-97407.png
A rock of mass m is dropped to the ground from a height h. A second rock with mass 2m is dropped from the same height. When second rock strikes the ground, what is its kinetic energy?
  • twice that of the first rock
  • four times that of the first rock
  • the same as that of the first rock
  • half that of the first rock
A bullet hits and gets embedded in a solid block resting on a frictionless surface. In this process which one of the following is correct?
  • Only momentum is conserved
  • Only kinetic energy is conserved
  • Neither momentum nor kinetic energy is conserved
  • Both momentum and kinetic energy are conserved
A car of mass m is driven with an acceleration a along a straight level road against a constant external resistive force R. When the velocity of the car is v, the rate at which engine of the car is doing work, will be
  • R ∙ v
  • ma ∙ v
  • (R + ma) ∙ v
  • (ma - R) ∙ v
An engine pumps up 100 kg of water through a height of 10m in 5 s. Given that the efficiency of engine is 60%. If g =10 ms-2, the power of the engine is
  • 3.3 kW
  • 0.33 kW
  • 0.033 kW
  • 33 kW
A block (B) is attached to two unstretched springs S1 and S2 with spring constants k and 4k, respectively (see Fig. (i)). The other ends are attached to identical supports M1 and M2 not attached to the walls. The springs and supports have negligible mass. There is no friction anywhere. The block B is displaced towards wall 1 by a small distance x (Fig. (ii)) and released. The block returns and moves a maximum distance y towards wall 2. Displacements x and y are measured with reect to the equilibrium position of the block B. The ratio y/x is
Physics-Work Energy and Power-97410.png
  • 4
  • 2

  • Physics-Work Energy and Power-97411.png

  • Physics-Work Energy and Power-97412.png
An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range
  • 200 J – 500 J
  • 2 × 105 J – 3 × 105 J
  • 20000 J – 50000 J
  • 2000 J – 5000 J
A river of salty water is flowing with a velocity 2 ms-1. If the density of the water is 1.2 g/cc, then the kinetic energy of each cubic metre of water is
  • 2.4 J
  • 24 J
  • 2.4 kJ
  • 4.8 kJ
Power applied to a particle varies with time as P = (3t2 – 2t + 1)W where, t is in second. Find the change in its kinetic energy between t =1 s and t = 4 s
  • 32 J
  • 46 J
  • 61 J
  • 102 J

Physics-Work Energy and Power-97417.png

  • Physics-Work Energy and Power-97418.png
  • 2

  • Physics-Work Energy and Power-97419.png

  • Physics-Work Energy and Power-97420.png

  • Physics-Work Energy and Power-97421.png
A spring gun of spring constant 90 Ncm-1 is compressed 12 cm by a ball of mass 16 g. If the trigger is pulled, the velocity of the ball is
  • 50 ms-1
  • 9 ms-1
  • 40 ms-1
  • 60 ms-1
  • 90 ms-1
A particle is moving under the influence of a force given by F = kx, where k is a constant and x is the distance moved. The energy (in joule) gained by the particle in moving from x=0 to x=3 is
  • 2k
  • 3.5k
  • 4.5k
  • 9k
  • 9.5k

Physics-Work Energy and Power-97425.png

  • Physics-Work Energy and Power-97426.png
  • 2)
    Physics-Work Energy and Power-97427.png

  • Physics-Work Energy and Power-97428.png

  • Physics-Work Energy and Power-97429.png
If the linear momentum is increased by 50%, then kinetic energy will be increased by
  • 50%
  • 20%
  • 125%
  • None of these
A long spring is stretched by 2 cm and its potential energy is U. If the spring is stretched by 10 cm, its potential energy will be
  • U/5
  • U/25
  • 5U
  • 25U
A bomb of mass 9 kg explodes into two parts. One part of mass 3 kg moves with velocity 16 m/s, then the kinetic energy of the other part is
  • 162 J
  • 150 J
  • 192 J
  • 200 J
A ball of mass 2 kg and another of mass 4 kg are dropped together from a 60 ft tall building. After a fall of 30 ft each towards the earth, their respective kinetic energies will be in the ratio of

  • Physics-Work Energy and Power-97434.png
  • 1 : 4
  • 1 : 2

  • Physics-Work Energy and Power-97435.png
A bomb of mass 3.0 kg explodes in air into two pieces of masses 2.0 kg and 1.0 kg. The smaller mass goes at a speed of 80 ms-1. The total energy imparted to the two fragments is
  • 1.07 kJ
  • 2.14 kJ
  • 2.4 kJ
  • 4.8 kJ
A spherical ball of mass 20 kg is stationary at the top of a hill of height 100 m. It rolls down a smooth surface to the ground, then climbs up another hill of height 30 m and height of 20 m above the ground. The velocity attained by the ball is
  • 40 ms-1
  • 20 ms-1
  • 10 ms-1

  • Physics-Work Energy and Power-97438.png
A particle is projected at 60° to the horizontal with a kinetic energy K. The kinetic energy at the highest point is
  • K
  • zero
  • K/4
  • K/2
A rubber ball is dropped from a height of 5 m on a planet, where the acceleration due to gravity is not known. On bouncing it rises to 1.8 m. The ball losses its velocity on bouncing by a factor of

  • Physics-Work Energy and Power-97441.png
  • 2)
    Physics-Work Energy and Power-97442.png

  • Physics-Work Energy and Power-97443.png

  • Physics-Work Energy and Power-97444.png
The kinetic energy of a body becomes four times its initial value. The new momentum will be
  • same as the initial value
  • twice the initial value
  • thrice the initial value
  • half of its initial value
The centripetal acceleration of a particle varies inversely with the square of the radius r of the circular path. The kinetic energy of this particle varies directly as
  • r
  • r2
  • r-2
  • r-1
A particle moves in a straight line with retardation proportional to its displacement. Its loss of kinetic energy for any displacement x is proportional to
  • x2
  • ex
  • x

  • Physics-Work Energy and Power-97448.png
When a spring is extended by 2 cm energy stored is 100 J. When extended by further 4 cm, the energy increases by
  • 400 J
  • 300 J
  • 200 J
  • 100 J
A block of mass m = 25 kg sliding on a smooth horizontal surface with a velocity v = 3 ms-1 meets the spring of spring constant k =100 Nm-1 fixed at one end as shown in figure. The maximum compression of the spring and velocity of block as it returns to the original position respectively are
Physics-Work Energy and Power-97451.png
  • 1.5 m, -3 ms-1
  • 1.5 m, 0.01 ms-1
  • 1.0 m , 3 ms-1
  • 0.5 m ,2 ms-1
Two springs of spring constants 1500 Nm-1 and 3000 Nm-1 respectively are stretched with the same force. They will have potential energy in ratio
  • 1 : 2
  • 2 : 1
  • 1 : 4
  • 4 : 1
A ball of mass 2 kg moving with velocity 3 ms-1, collides with spring of natural length 2m and force constant 144 Nm-1. What will be length of compressed spring?
  • 2 m
  • 1.5 m
  • 1 m
  • 0.5 m
A steel ball of mass 5 g is thrown downward with velocity 10 ms-1 from height 19.5 m. it penetrates sand by 50 cm. The change in mechanical energy will be (take, g =10ms-2 )
  • 1 J
  • 1.25 J
  • 1.5 J
  • 1.75 J
To the free end of spring hanging from a rigid support, a block of mass m is hung and slowly allowed to come to its equilibrium position. Then stretching in the spring is d. If the same block is attached to the same spring and allowed to fall suddenly, the amount of stretching is (force constant, k)

  • Physics-Work Energy and Power-97456.png
  • 2d

  • Physics-Work Energy and Power-97457.png
  • 4d
The upper half of an inclined plane with inclination ϕ is perfectly smooth, while the lower half is rough. A body starting from rest at the top will again come to rest at the bottom, if the coefficient of friction for the lower half is given by
  • 2 sin ϕ
  • 2 cos ϕ
  • 2 tan ϕ
  • tan ϕ
The block of mass M moving on the frictionless horizontal surface collides with the spring of spring constant k and compresses it by length L The maximum momentum of the block after collision is
Physics-Work Energy and Power-97460.png

  • Physics-Work Energy and Power-97461.png
  • 2)
    Physics-Work Energy and Power-97462.png
  • zero

  • Physics-Work Energy and Power-97463.png
At time t = 0 s particle starts moving along the x–axis. If its kinetic energy increases uniformly with time t,the net force acting on it must be proportional to

  • Physics-Work Energy and Power-97465.png
  • constant
  • t

  • Physics-Work Energy and Power-97466.png
A box is moved along a straight line by a machine delivering constant power. The distance moved by the body in time t is proportional to
  • t1/2
  • t3/4
  • t3/2
  • t2
A body of mass M is moving with a uniform speed of 10m/s on frictionless surface under the influence of two forces F1 and F2. The net power of the system is
  • 10F1F2M
  • 10(F1 + F2)M
  • (F1 + F2)M
  • zero
Two balls at same temperature collide. What is conserved?
  • Temperature
  • Velocity
  • Kinetic energy
  • Momentum
An electric pump is used to fill an overhead tank of capacity 9 m3 kept at a height of 10 m above the ground. If the pump takes 5 min to fill the tank by consuming 10 kW power the efficiency of the pump should be (take, g = 10 ms-1 )
  • 60%
  • 40%
  • 20%
  • 30%
  • 50%
An engineer claims to have made an engine delivering 10kW power with fuel consumption of 1 gs-1. The calorific value of fuel is 2 Kcalg-1. This claim is
  • valid
  • invalid
  • dependent on engine design
  • dependent on load
A body of mass 2 kg is projected at 20 ms-1 at an angle 60° above the horizontal. Power due to the gravitational force at its highest point is
  • 200 W
  • 2)
    Physics-Work Energy and Power-97473.png
  • 50 W
  • zero
A motor is used to deliver water at a certain rate through a given horizontal pipe. To deliver n times the water through the same pipe in the same time the power of the motor must be increased as follows
  • n times
  • n3 times
  • n4 times
  • n2 times
The machine gun fires 240 bullets per minute. If the mass of each bullet is 10 g and the velocity of the bullets is 600 ms-1 , the power (in kW) of the gun is
  • 43200
  • 432
  • 72
  • 7.2
If the heart pushes 1 cc of blood in 1 s under pressure 20000 Nm-2, the power of heart is
  • 0.02 W
  • 400 W
  • 5 × 10-10 W
  • 0.2 W
A man does a given amount of work in 10 s. Another man does the same amount of work in 20 s. The ratio of the output power of first man to the second man is
  • 1
  • 1/2
  • 2/1
  • None of these
In elastic collision,
  • both momentum and kinetic energy are conserved
  • neither momentum nor kinetic energy is conserved
  • only momentum is conserved
  • only kinetic energy is conserved
  • forces involved in interaction and non-conservative
A block of mass 0.50 kg is moving with a speed of 2 ms -1 on a smooth surface. It strikes another mass of 1kg and then they move together as a single body. The energy loss during the collision is
  • 0.16 J
  • 1.00 J
  • 0.67 J
  • 0.34 J
A ball is dropped from a height h on a floor of coefficient of restitution e. The total distance covered by the ball just before second hit is
  • h(1 – 2e2 )
  • h(1 + 2e2 )
  • h(1 + e2 )
  • he2
Two identical mass m moving with velocities u1 and u2 collide perfectly inelastically. Find the loss in energy

  • Physics-Work Energy and Power-97481.png
  • 2)
    Physics-Work Energy and Power-97482.png

  • Physics-Work Energy and Power-97483.png

  • Physics-Work Energy and Power-97484.png
Statement I In an elastic collision between two bodies, the relative speed of the bodies after collision is equal to the relative speed before the collision.
Statement II In an elastic collision, the linear momentum of the system is conserved.
  • Statement I is correct, statement II is correct, statement II is a correct explanation for statement I
  • Statement I is correct, statement II is correct, statement II is incorrect explanation for statement I
  • Statement I is correct, statement II is incorrect
  • Statement I is incorrect, statement II is correct
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