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CBSE Questions for Class 11 Engineering Physics Work,Energy And Power Quiz 9 - MCQExams.com

A bod of mass M is suspended by a massless string of length L.The horizontal velocity V at position A is just sufficient to make real the point B.The angle θ at which the speed of the bob is half of that it A satisfies:
1270979_917d575b5ec54ed1b84b2a7ffa04ba11.png
  • θ=π4
  • π4<θ<π2
  • π2<θ<3π4
  • 3π4<θ<π
A body of mass 1 kg begins to move under the action of a time dependent  force F=(2tˆi+3t2ˆj) N, where ˆi and ˆj are unit vectors along x and y axes. What power will be developed by the force at the time t?
  • (2t2+3t2)W
  • (2t4+4t4)W
  • (2t3+3t4)W
  • (2t3+3t5)W
Two wires of the same diameter of the same material having the length and 2. If the force is applied on each, the ratio of the work done in the two will be
  • 1:2
  • 1:4
  • 2:1
  • 1:1
By applying a force F=(3xy5z)j+4zk a particle is moved along the path y=x2 from point (0,0,0) to the point (2,4,0). The work done by the F on the particle is (all values are in SI units)
1270771_88cb9d01112c47d38e7adb03c6428eff.png
  • 2805J
  • 1405J
  • 2325J
  • 1925J
Two masses 10 gm and 40 gm are moving with kinetic energies in the ratio 9:25. The ratio of their linear momentum is:
  • 5:6
  • 3:10
  • 6:5
  • 10:3
A force is acting on a particle varies with the displacement x as F=axbx2. Where a=1 N/m and b=1N/m2. The work done by this force for the first one meter (F is in newtons, x is in meters) is :
  • 16J
  • 26J
  • 36J
  • None of these
The work done in placing a charge of 8×1018 coulomb on a condenser of capacity 100 micro-farad is 
  • 16×1032 joule
  • 3.2×1026 joule
  • 4×1010 joule
  • 32×1032 joule
A particle of mass 1 kg is projected under gravity at an angle 37o with horizontal with 50 m/s. Instantaneous power delivered by gravity at t=1s is (sin37o=35,cos37o=45)
  • 200 J/s
  • -200 J/s
  • Zero
  • -400 J/s
Mass of B is four times that of A.B moves with a velocity half that of A. Then, B has 
  • kinetic energy equal to that of A
  • half the kinetic energy of A
  • twice the kinetic energy of A
  • kinetic energy one-fourth of A
A particle is moving in a vertical circle. The tension in the string when passing through two positions at angles 30o and 60o from vertical (lowest position) are T1 and T2 respectively, then
  • T1=T2
  • T2>T1
  • T1>T2
  • tension in the string always remains the same
A body of mass 2 kg moving under a force has relation between displacement x and time t as x=t33 where x is in metre and t is in sec. The work done by the body in first two second will be
  • 1.6 joule
  • 16 joule
  • 160 joule
  • 1600 joule
Work done by a force F=(ˆi+2ˆj+3ˆk) N action on a particle in displacing it from the point r1=ˆi+ˆj+ˆk to the point r1=ˆiˆj2ˆk
  • 1 J
  • 2 J
  • 13 J
  • zero
A particle moves along positive X-axis from x=0 to x=5 under influence of force is given byF=x22x8. The work done by the force is 
  • -69 units
  • -23.33 units
  • -5 units
  • zero
The displacement (x) and time (t) for a particle are related as t=x+3. What is the work done in the first six second of its motion?
  • 3 J
  • 4 J
  • Zero
  • 5 J
Five identical balls each of mass m and radius r are strung like beads at random and at rest along a smooth, rigid horizontal thin rod of length L, mounted between immovable supports. Assume 10r<L and that the collision between balls or between balls and supports are elastic. If one ball is struck horizontally so as to acquire a speed v, the average force felt by the support is 
1299290_d7b92577c587474fa13923eeaaeb0893.PNG
  • 5mL5r
  • mv2L10r
  • 5mv2L10r
  • mv2L5r
When a 4 kg mass is hung vertically on a light spring obey's Hooks law , the spring stretches by 2 cms. The work required to be done by an external agent in stretching this spring by 5 cm will be ( g =9.8 ms2 )
  • 4.9 J
  • 2.4 J
  • 0.495 J
  • 0.24 J
A position dependent force F=72x+3x2 newton acts on a small body of mass 2kg and displaces it from x=0 to x=5. The work done in joule is :
  • 70
  • 270
  • 35
  • 135
Two bodies of masses 4kg and 16kg are at rest. The ratio of times for which the same force must act on them to produce the same kinetic energy in both of them is
  • 1:4
  • 2:1
  • 1:2
  • 4:1
F=xˆi+yˆj, is this force:
  • a conservation force
  • a non conservation
  • depends upon X
  • depends upon y&x
 A force of 1200N acting on a stone by means of a rope slides the stone through a distance{ of10min a direction inclined at 60 force. The work done by the force is
  • 60003J
  • 6000 J
  • 12000 J
  • 8000 J
 A man weighing 80kg climbs a staircase  carrying a 20kg load. The staircase has 40 steps, each of 25cm height. If he takes 20 seconds to climb, the work done is 
  • 9800J
  • 245J
  • 98×104J
  • 7840 J
The tension in the string revolving in a vertical circle with a mass m at the end which is at the lowest position  
  • mv2r
  • mv2rmg
  • mv2r+mg
  • mg

The work done by a force F=(6x3ˆi) in displacing a particle from x=4m to x=2m is:     

  • 240 J
  • 360 J
  • 420J
  • will depend upon the path
A variable force given by F=(3x2ˆi+4ˆj) acts on a particle. the force is in newton and x is in meter. what is the change in KE of particle as it moves from point (2, 3) to (3, 0) 
  • -7J
  • zero
  • 7J
  • 19J
Work done by air when it expands from 50 litres to 150 litres at a constant pressure of 2 atmospheres is:
  • 2×104J
  • 2×100J
  • 2×105×100J
  • 2×10.5×100J
does not vary from point to point in space Which pair of the following forces will never give resultant force of 2 N?
  • 1 N and 3 N
  • 2 N and 2 N
  • 1 N and 1 N
  • 1 N and 4 N
A force F1 on a body of 2 kg produces an acceleration of 2.5m/m2 and other force F2 acting on another body of mass 5 kg produces an acceleration of 2m/s2. The ratio of F2/F1 is
  • 2
  • 4
  • 6
  • 8
A hollow smooth uniform sphere A of mass m rolls without sliding on a smooth horizontal surface. It collides elastically and head-on with another stationary smooth hollow sphere B of the same mass mm and same radius. The ratio of the kinetic energy of B to that of A just after the collision is 
1361865_11e6976e511a4024abd91ae2aaca3faf.PNG
  • 1:1
  • 2:3
  • 3:2
  • None
The speed of a motor increases from 1200 rpm to 1800 rpm in 20 s. How many revolutions does it make during these second?
  • 400
  • 600
  • 500
  • 700
If body of mass 2 kg is moving along X axis under an external force, whose displacement is given by x(t)=3t22t+5m. Find the work done by force from t = 0 to t = 5 sec.
  • 78J
  • 780J
  • 840J
  • 200J

AB is long frictionless horizontal surface. One end of an ideal spring of spring constant K is attached to a block of mass m, which is being moved left moved left with constant velocity v, and another end is free.Another block of mass 2m is given a velocity 3v towards the spring. Work done by an external agent in moving m with constant velocity v in a long time will be:

  • 5mv2
  • 8mv2
  • 3mv2
  • None of these
A force F=2xˆi+3y2ˆjN where x and y are in meter, acts upon a particle. Find work done (in J) by this force in displacing the particle from (1 m, 2 m, 5 m) to (2 m, 3 m, 2 m).
  • 24
  • 16
  • 28
  • 22
When a simple pendulum is rotated in a vertical plane with constant angular velocity, centripetal force is:
  • maximum at highest point
  • maximum at lowest point
  • same at all points
  • zero
In the figure, at the free end of the light string, a force F is applied to keep the suspended mass of 18\mathrm { kg }$$ at rest. Assuming



1402949_aca715d872ac4b2caeb287507171715b.png
  • 240N
  • 120M
  • 180M
  • 240M
A block of mass 10 kg is moving up on an inclined plane with constant acceleration 2 m/sec by applying a constant force F as shown in the fig. The work done on the block by applied force F in 2 s is
1392596_8ea8b2aa4e354531ac6c0508ebcbd0e6.png
  • 480
  • 240
  • 960
  • none
A force F=(3x2+2x7) N acts on a 2 kg body as a result of which the body gest displaced x=0 to x=5 cm. The work done by the force will be-
  • 35 Joule
  • 70 Joule
  • 115 Joule
  • 270 Joule
A particle moves along the x-axis from x=0 to x=5 m under the influence of a force given by F=(72x+3x2)N. The work done in the process is
  • 70 J
  • 270 J
  • 35 J
  • 135 J
The amount of work done in stretching a wire by 10N force can cause an elongation of 2×102m will be 
  • 10 J
  • 1 J
  • 0.1 J
  • 0.01
Velocity-time graph of a particle of mass 2 kg moving in a straight line is as shown in figure. Work done by all the forces on the particle during the motion is:
1392827_e49dbb3dfa6a4ecc918b83069c161981.JPG
  • 400J
  • 400J
  • 200J
  • 200J
A particle is displaced from a position (2ˆiˆj+ˆk) metre to another position (3ˆi+2ˆj2ˆk) meter under the action of force (2ˆi+ˆjˆk) N. Work done by the force is:
  • 8 J
  • 10 J
  • 12 J
  • 36 J
A cone filled with water is whirled in a vertical circle of radius 4 m. What will be the time period of rotation so that water does not fall ?
  • 4 s
  • 6 s
  • 2 s
  • 1 s
A balloon with its contents weighing 160 N is moving down with an acceleration of g/2 ms2 the mass to be removed from it so that the balloon moves up with an acceleration of g/3ms2 is 
  • 5 kg
  • 10 kg
  • 6 kg
  • 3 kg
In 10s, a body of 6kg mass is dragged 8m with uniform velocity across a floor by a steady force of 20N. The K.E of the body is:
  • 2.92J
  • 0.92J
  • 1.92J
  • 0J
The breaking strength of a string is 55 kg wt. The maximum permissible speed of a stone of mass 5 kg which revolved in a vertical circle of radius 4 m with the help of is the string is g=10 s2.
  • 10m/sec
  • 15m/sec
  • 20m/sec
  • 25m/sec
A force of (4x2+3x) N acts on a particle which displaces it from x=2m to x=3m.
The work done by the force is
  • 32.8J
  • 3.28J
  • 0.328J
  • zero
A body of mass m is rotating in a vertical circle of radius 'r' with critical speed. The difference in its K.E. at the top and the bottom is _____.
  • 2mgr
  • 4 mgr
  • 6 mgr
  • 3 mgr
A spring of force constant 800N/m has an extension of 5cm. The work done in extending it from 5cm to 15cm is :
  • 16J
  • 8J
  • 32J
  • 24J
Two springs of force constants K1 and K2 (K1>K2) are stretched by same force. If W1 and W2 be the work done stretching the springs then
  • W1=W2
  • W1<W2
  • W1>W2
  • W1=W2=0
A vertical spring of force constant 100N/m is attached with a hanging mass of 10kg. Now an external force is applied on the same so that the spring is stretched by additional 2m. The work done by the force is (g=10m/s2)
1431733_656c2220f8e945e68795cc6f8812bf8c.png
  • 200J
  • 400J
  • 450J
  • 600J
At the instant speed of block is maximum, the magnitude of force exerted by spring on the block is
1433820_5df2a0e6894142068553c4a15c8a1b98.png
  • mg2
  • mg
  • Zero
  • None of these
0:0:1


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