NEET UG Physics Laws of Motion MCQs

Asseration and reason type question
Asseration and reason are given in following question. Each question have four options. One of them is  correct select it.
(a) Asseration is true. Reason is true and reason is correct explanatin for Assertion.
(b) Asseration is true. Reason is ture but reason is not the correct explanatin of assertion.
(c) Asseration is ture. Reason is false.
(d) Asseration is false. Reason is true.

81. Asseration : Frictional forces are conservative forces.
      Reason : Potential energy can be associated with frictional forces.
(A) a
(B) b
(C) c
(D) d

82. Asseration : A body of mass 1 kg is moving with an accelaration of 1ms^-1 . The rate of change of its momentum is 1 N.
      Reason : The rate of change of momentum of body = force applied on the body.
(A) a
(B) b
(C) c
(D) d

83. Asseration : A body falling freely under gravity becomes weightless.
      Reason : R = m(g – a) = m(g – g) = 0
(A) a
(B) b
(C) c
(D) d

84. Asseration : It is difficult to move bike with its breaks on.
      Reason : Rolling friction is converted into sliding friction, which is comparatively larger.
(A) a
(B) b
(C) c
(D) d

Comprehension :-
According to newton's second low of mation, F= ma, where F is the force required to produce an accelaration a in a body of mass m. If a = 0 than F = 0. If a force acts on a body for t seconds, the effect of the force is given by impulse = F × t = change in linear momentum of the body.with the help of the passage given above, choose the most appropriate alternative for each of the following questions.

85 A cricket ball of mass 150 g. is moving with a velocity of 12 m/s and is hit by a bat so that the ball is turned back with a velocity of 20 m/s. If duration of contact between the ball and the bat is 0.01 sec. The impulse of the force is
(A) 7.4 NS
(B) 4.8 NS
(C) 1.2 NS
 (D) 4.7 NS

86. Average force exerted by the bat is
(A) 480 N
(B) 120 N
(C) 1200 N
(D) 840 N

87. The force acting on a body whose linear momentum changes by 20 kgms^-1 in 10 sec is
(A) 2 N
(B) 20 N
(C) 200 N
(D) 0.2 N

88. An impulsive force of 100 N acts on a body for 1 sec What is the change in its linear momentum ?
(A) 10 N-S
(B) 100 N-S
(C) 1000 N-S
(D) 1 N-S