Force of Friction

Comprehension

Passage I

A man uses a rope to vertically lower an initially stationary block of mass M at a constant downward acceleration of g/4. Let the block has fallen through a distance `y'.

Question 31: The work done by the tension in the rope on the block is given by—

  1. -Mgy

Answer: (a)

Question 32: The final value of kinetic energy of the block is—

  1. Mgy
  2. 2Mgy

Answer: (c)2Mgy

Question 33: Final speed of motion of block is—

Answer: (c)

Passage II

A small particle of mass m is released from a height H on a smooth curved inclined surface, which ends into a vertical loop of radius R as shown in adjoining Fig. The initial velocity of particle was zero.

Question 34: Choose the correct statement if value of H = 2R.

  1. The particle easily completes the vertical loop
  2. The particle reaches the top of the loop with zero velocity
  3. The particle breaks off at a height h = R from the base of the loop
  4. The particle breaks off at a height R < h < 2R

Answer: (d) The particle breaks off at a height R < h < 2R

Passage III

An object of mass 2 kg is lying at rest on a smooth floor. When a force F is applied on it, the object begins to move in the direction of force applied. The force is a variable force. Variation of force F with distance covered by the object has been shown in adjoining figure.

Question 35: The maximum kinetic energy of the object is—

  1. 15 J
  2. 35 J
  3. 17.5 J
  4. 20 J

Answer: (c) 17.5 J

Question 36: At s = 7 m—

  1. K.E. of the object is negative
  2. K.E. of the object is positive
  3. speed of the particle is zero
  4. Nothing is certain

Answer: (b) K.E. of the object is positive


Copyright © excellup 2014