Engineering Physics Multiple Choice Questions on “Moment of Inertia”.
1. A gun fires a bullet of mass 50g with a velocity of 30m/s. Because of this, the gun is pushed back with a velocity of 1m/s. The mass of the gun is?
a) 5.5kg
b) 3.5kg
c) 1.5kg
d) 0.5kg
Answer: c
Clarification: By conservation of momentum, MV = mv
M = mv/V = 1.5kg.
2. A body of mass 5kg is raised vertically to a eight of 10m by a force of 170N. The velocity of the body at this height will be ___________
a) 37m/s
b) 22m/s
c) 15m/s
d) 9.8m/s
Answer: b
Clarification: W = Gain in potential energy+Gain in kinetic energy
Fh = mgh + 1/2 mv2
170×10=5×10×10+1/2×5×v2
v = √480 = 22m/s.
3. A position dependent force, F = 7-2x+3x2-N acts on a small body of mass 2kg and displaces it from x = 0 to x = 5m. The work done in joules is ___________
a) 135
b) 270
c) 35
d) 70
Answer: a
Clarification: W = ∫Fdx = (int_0^5 (7-2x+3x^2)dx = [7x-x^2+x^3]_0^5)
W = 35-25+125=135J.
4. A particle of mass M is moving in a horizontal circle of radius R with uniform speed v. When it moves from one point to a diametrically opposite point, its ___________
a) Kinetic energy changes by (Mv)2/4
b) Momentum does not change
c) Momentum changes by 2Mv
d) Kinetic energy changes by (Mv)2
Answer: c
Clarification: At any two diametrically opposite points, velocities of the particle have the same magnitude but opposite directions. Therefore change in momentum = Mv-(-MV)=2Mv.
5. Two identical balls A and B collide head on elastically. If velocities of A and B, before the collision are +0.5m/s and -0.3m/s respectively, then the velocities after the collision, are ___________
a) -0.5m/s and +0.3m/s
b) +0.5m/s and +0.3m/s
c) +0.3m/s and -0.5m/s
d) -0.3m/s and +0.5m/s
Answer: d
Clarification: In an elastic collision between two bodies of equal masses, velocities get exchanges after collision. vA=-0.3m/s and vB=+0.5m/s.
6. The kinetic energy acquires by a mass m in travelling distance d, starting from rest, under the action of a constant force is directly proportional to ___________
a) m
b) m0
c) √m
d) 1/√m
Answer: b
Clarification: v2-u2=2as
v2-0=2×F/m×d = 2Fd/m
Kinetic energy = 1/2 mv2=1/2 m×2Fd/m = Fd
Hence, kinetic energy does not depend on m or it is directly proportional to m0.
7. A simple pendulum hanging freely and at rest is vertical because in that position ___________
a) Kinetic energy is zero
b) Potential energy is zero
c) Kinetic energy is minimum
d) Potential energy is minimum
Answer: d
Clarification: In the position of equilibrium, the potential energy of the simple pendulum is minimum. Therefore a simple pendulum hanging freely and at rest is vertical because in that position potential energy is minimum.
8. A bullet is fired and gets embedded in a block kept on the table. If a table is frictionless, then ___________
a) Kinetic energy gets conserved
b) Potential energy gets conserved
c) Momentum gets conserved
d) Kinetic energy and potential energy gets conserved
Answer: c
Clarification: Only momentum gets conserved when a bullet is fired and gets embedded in a block kept on a frictionless table. Some kinetic energy is lost when the bullet penetrates the block.
9. A ball moves in a frictionless inclined table without slipping. The work done by the table surface on the ball is ___________
a) Positive
b) Negative
c) Zero
d) Infinity