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Set 8 of 10 · Questions 211-240 of 294

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JEE Main Physics · Work, Energy & Power · Set 8 (Q211-240)

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  1. 211.
    A body of mass 'm' dropped from a height 'h' reaches the ground with a speed of . The value of work done by the air-friction is:
    1. (1)-0.68mgh
    2. (2)mgh
    3. (3)1.64mgh
    4. (4)0.64mgh
  2. 212.
    An object of mass 500 g, initially at rest, is acted upon by a variable force whose X-component varies with X in the manner shown. The velocities of the object at the points X = 8 m and X = 12 m, would have the respective values of (nearly)
    1. (1)18 m/s and 24.4 m/s
    2. (2)23 m/s and 24.4 m/s
    3. (3)23 m/s and 20.6 m/s
    4. (4)18 m/s and 20.6 m/s
  3. 213.
    A body of mass is lying in x‐y plane at rest. It suddenly explodes into three pieces. Two pieces, each of mass (m) move perpendicular to each other with equal speeds (v). The total kinetic energy generated due to explosion is
    1. (1)
    2. (2)
    3. (3)
    4. (4)
  4. 214.
    A particle moves from a point to when a force of is applied. How much work has been done by the force
    1. (1)2J
    2. (2)8 J
    3. (3)11 J
    4. (4)5 J
  5. 215.
    A ball of mass moving horizontally at strikes a vertical wall and rebounds with speed . The magnitude of the change in linear momentum is found to be . The magnitude of is
    1. (1)
    2. (2)
    3. (3)
    4. (4)
  6. 216.
    The ratio of powers of two motors is , that are capable of raising 300 kg water in 5 minutes and 50 kg water in 2 minutes respectively from a well of 100 m deep. The value of x will be
    1. (1)16
    2. (2)2
    3. (3)2.4
    4. (4)4
  7. 217.
    A point mass is moved in a vertical circle of radius with the help of a string. The velocity of the mass is at the lowest point. The tension in the string at the lowest point is [NEET 2020]
    1. (1)6 mg
    2. (2)7 mg
    3. (3)8 mg
    4. (4)1 mg
  8. 218.
    The bob of a pendulum was released from a horizontal position. The length of the pendulum is . If it dissipates of its initial energy against air resistance, the speed with which the bob arrives at the lowest point is : [Use, ]
    1. (1)
    2. (2)
    3. (3)
    4. (4)
  9. 219.
    A body of slides from rest along the curve of vertical circle from point A to B in friction less path. The velocity of the body at B is:

    (given, and )
    1. (1)
    2. (2)
    3. (3)
    4. (4)
  10. 220.
    A time varying force acts on a ball of mass for . The force versus time curve is shown below. If the initial speed of the ball is , then the speed of ball after is
    1. (1)
    2. (2)
    3. (3)
    4. (4)
  11. 221.
    The work done by a force acting on a body is as shown in the graph. The total work done in covering an initial distance of is
    1. (1)
    2. (2)
    3. (3)
    4. (4)
  12. 222.
    A particle is moving in a circular path of radius a under the action of an attractive potential U = – . Its total energy is:
    1. (1)zero
    2. (2)
    3. (3)
    4. (4)
  13. 223.
    In the given figure, the block of mass m is dropped from the point 'A'. The expression for kinetic energy of block when it reaches point 'B' is:
    1. (1)
    2. (2)
    3. (3)mg (y - )
    4. (4)
  14. 224.
    Force on a particle moving in a straight line varies with distance as shown in figure.

    The work done on the particle during its displacement of 12 is
    1. (1)18
    2. (2)21
    3. (3)26
    4. (4)13
  15. 225.
    A block of mass m is kept on a platform which starts from rest with constant acceleration g/2 upward, as shown in figure. Work done by normal reaction on block in time t is:
    1. (1)
    2. (2)0
    3. (3)
    4. (4)
  16. 226.
    A particle of mass 500 gm is moving in a straight line with velocity u = . The work done by the net force during its displacement from x = 0 to x = 4 mis: (Take b = 0.25 ).
    1. (1)2J
    2. (2)4J
    3. (3)8 J
    4. (4)16 J
  17. 227.
    A body initially at rest and sliding along a frictionless track from a height h (as shown in the figure) just completes a vertical circle of diameter . The height h is equal to (NEET2018)
    1. (1)
    2. (2)D
    3. (3)
    4. (4)
  18. 228.
    Particle moves from point A to point B along the line shown in figure under the action of force. . Determine the work done on the particle by in moving the particle from point A to point B
    1. (1)1J
    2. (2)
    3. (3)2J
    4. (4)3J
  19. 229.
    On a frictionless surface, a block of mass moving at speed collides elastically with another block of same mass which is initially at rest. After collision the first block moves at an angle 6 to its initial direction and has a speed . The second block’s speed after the collision is
    1. (1)
    2. (2)
    3. (3)
    4. (4)
  20. 230.
    A body of mass 100 g is moving in circular path of radius 2 m on vertical plane as shown in
    figure. The velocity of the body at point is . The ratio of its kinetic energies at point and is :

    (Take acceleration due to gravity as )
    1. (1)
    2. (2)
    3. (3)
    4. (4)
  21. 231.
    A mass of 0.5 kg moving with a speed of 1.5 on a horizontal smooth surface, collides with a nearly weightless spring of force constant . The maximum compression of the spring would be
    1. (1)0.15
    2. (2)0.12
    3. (3)1.5
    4. (4)0.5
  22. 232.
    A block moving horizontally on a smooth surface with a speed of splits into two equal parts. If one of the parts moves at in the same direction, then the fractional change in the kinetic energy will be x:4, where x =.....
  23. 233.
    A block of mass 'm' (as shown in figure) moving with kinetic energy E compresses a spring through a distance 25 cm when, its speed is halved. The value of spring constant of used spring will be nE for n = _______
  24. 234.
    A ball of mass 100 g is dropped from a height h = 10 cm on a platform fixed at the top of vertical spring (as shown in figure). The ball stays on the platform and the platform is depressed by a distance . The spring constant is________. (Use g = 10 )
  25. 235.
    A hollow spherical ball of uniform density rolls up a curved surface with an initial velocity 3 m (as shown in figure). Maximum height with respect to the initial position covered by it will be_____cm (take, g = 10 m )
  26. 236.
    A car accelerates from rest of u m . The energy spent in this process is E J. The energy required to accelerate the car from u m to 2u m is nE J. The value of n is_____.
  27. 237.
    A circular table is rotating with an angular velocity of about its axis (see figure). There is a smooth groove along a radial direction on the table. A steel ball is gently placed at a distance of 1 m on the groove. All the surfaces are smooth. If the radius of the table is 3 m, the radial velocity of the ball w.r.t. the table at the time ball leaves the table is , where the value of is …………..
  28. 238.
    As shown in the figure, a particle of mass is placed at a point When the particle is slightly displaced to its right, it starts moving and reaches the point The speed of the particle at is . (TakeThe value of to the nearest integer is .
  29. 239.
    A light inextensible string that goes over a smooth fixed pulley as shown in the figure connects two blocks of masses 0.36 kg and 0.72 kg. Taking g = 10 m/, find the work done (in joules) by the string on the block of mass 0.36 kg during the first second after the system is released from rest.
  30. 240.
    A particle () slides down a frictionless track () starting from rest at a point (height ). After reaching , the particle continues to move freely in air as a projectile. When it reaching its highest point (height ), the kinetic energy of the particle (in ) is: (Figure drawn is schematic and not to scale; take )