Work, Energy And Power CBSE Questions & Answers

Work, Energy And Power

This is Physics Class 11 Work, Energy and Power CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

1
The potential energy of a spring whose spring constant is k and is compressed by x is
  • A
    \({1 \over 4}k{x^2}\)
  • B
    \(k{x^2}\)
  • C
    \({1 \over 2}k{x^2}\)
    Correct
  • D
    \(k{x^2}\)2
2
mass and energy are equivalent and are related by
  • A
    \(E = m{c^2}/2\)
  • B
    \(E = m{c^3}\)
  • C
    \(E = m{c^2}\)
    Correct
  • D
    \(E = 2m{c^2}\)
3
Power is defined as
  • A
    the time rate at which work is done or energy is transferred
    Correct
  • B
    ability to do work
  • C
    stored energy
  • D
    the time at which work is done or energy is transferred
4
S.I unit of power is
  • A
    Angstrom
  • B
    Watt
    Correct
  • C
    Newton
  • D
    Joule
5
Which of the following laws used to solve problems in collisions?
  • A
    kepler’s laws
  • B
    Kirchhoff’s laws
  • C
    laws of momentum and energy conservation
    Correct
  • D
    Newton’s laws
6
in an elastic collision
  • A
    the total kinetic energy of the system is less than the total kinetic energy before
  • B
    the total kinetic energy of the system is the zero after the collision.
  • C
    the total kinetic energy of the system is greater than the total kinetic energy before
  • D
    the total kinetic energy of the system is the same after the collision as before.
    Correct
7
in an inelastic collision
  • A
    the total kinetic energy after the collision is less than before the collision
    Correct
  • B
    the total kinetic energy of the system is greater than the total kinetic energy before
  • C
    the total kinetic energy of the system is the same after the collision as before
  • D
    the total kinetic energy of the system is the zero after the collision.
8
In a completely inelastic collision
  • A
    the colliding bodies stick together and move as one body after the collision
    Correct
  • B
    the colliding bodies move in same direction after the collision
  • C
    the colliding bodies move at an angle after the collision
  • D
    the colliding bodies move in opposite directions after the collision
9
Considering a completely inelastic collision of a particle of mass \({{\text{m}}_{\text{1}}}\) moving with initial velocity \({{\text{v}}_{\text{2}}}\) and a stationary particle of mass \({{\text{m}}_{\text{2}}}\)the final velocity is given by
  • A
    \({{{m_1}} \over {{m_1} + 2{m_2}}}{v_1}\)
  • B
    \({{{m_1}} \over {2{m_1} + {m_2}}}{v_1}\)
  • C
    \({{{m_2}} \over {{m_1} + {m_2}}}{v_1}\)
  • D
    \({{{m_1}} \over {{m_1} + {m_2}}}{v_1}\)
    Correct
10
Considering a completely inelastic collision of a particle of mass \({{\text{m}}_{\text{1}}}\)moving with initial velocity \({{\text{v}}_{\text{1}}}\) and a stationary particle of mass \({{\text{m}}_{\text{2}}}\) The ratio of final to initial kinetic energy is
  • A
    \({{{m_1}} \over {{m_1} + {m_2}}}\)
    Correct
  • B
    \({{{m_2}} \over {{m_1} + {m_2}}}\)
  • C
    \({{{m_1}} \over {{m_1} + 2{m_2}}}\)
  • D
    \({{{m_1}} \over {2{m_1} + {m_2}}}\)
11
In which of the following cases is the work done positive?
  • A
    Work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket.
    Correct
  • B
    Work done by gravitational force while a man in lifts a bucket out of a well by means of a rope tied to the bucket
  • C
    Work done by the resistive force of air on a vibrating pendulum in bringing it to rest.
  • D
    Work done by friction on a body sliding down an inclined plane
12
A body of mass 2 kg initially at rest moves under the action of an applied horizontal force of 7 N on a table with coefficient of kinetic friction = 0.1.Compute the (a) work done by the applied force in 10 s,(b) work done by friction in 10 s.
  • A
    842 J, 247 J
  • B
    800 J, -207 J
  • C
    822 J, 247 J
  • D
    882 J, -247 J
    Correct
13
A body of mass 2 kg initially at rest moves under the action of an applied horizontal force of 7 N on a table with coefficient of kinetic friction = 0.1. Compute the (a) work done by the net force on the body in 10 s,(b) change in kinetic energy of the body in 10 s
  • A
    635 J, 635 J
    Correct
  • B
    600 J, 600 J
  • C
    555 J, 555 J
  • D
    655 J, 655 J
14
The casing of a rocket in flight burns up due to friction. At whose expense is the heat energy required for burning obtained?
  • A
    atmosphere
  • B
    reaction force energy
  • C
    Rocket
    Correct
  • D
    earth’s gravitational energy
15
A body constrained to move along the z-axis of a coordinate system is subject to a constant force F given by \({\bf{F}} = - {\bf{\hat i}} + + 2{\bf{\hat j}} + 3{\bf{\hat k}}{\rm{N}}\), where \(\hat i,{\rm{\hat jand\hat k}}\) are unit vectors along the x-, y- and z-axis of the system respectively. What is the work done by this force in moving the body a distance of 4 m along the z-axis?
  • A
    7 J
  • B
    15 J
  • C
    9 J
  • D
    12 J
    Correct