1. Coefficient of restitution of elastic bodies is ______
a) One
b) More than one
c) Between 0 and one
d) zero
Explanation: In case of elastic bodies the relative velocity after collision is equal to the relative velocity before collision, hence the coefficient of restitution is 1.
2. Kinetic energy before collision is always equal to the kinetic energy after collision
a) true
b) false
Explanation: Kinetic energy before collision is equal to the kinetic energy after collision only in case of elastic collisions, in other cases energy is lost during deformation
3. Which of the following cases has the greatest loss in Kinetic energy?
a) e=0
b) e=1/2
c) e=1/4
d) e=1
Explanation: e=0 signifies that the collision was completely inelastic, in case of completely inelastic collisions the Kinetic energy loss after collision is maximum.
4. A sphere of mass 25 Kg is moving at a speed of 1.5 m/s undergoes collision with another sphere of mass 50 Kg moving at 3m/s in the same direction, find the velocity of 25 Kg mass in m/s after collision when the collision is elastic.
a) 2.5
b) 2.00
c) 3.5
d) 6.75
Explanation: Velocity during elastic collision is given by
m1u1 + m2u2/(m1+ m2) = v
substituting the values we get
V = 2.5 m/s
v2 = 2V – u2
v2 = 3.5 m/s
5. A sphere of mass 25 Kg is moving at a speed of 1.5 m/s undergoes collision with another sphere of mass 50 Kg moving at 3m/s in the same direction, find the velocity of 25 Kg mass in m/s after collision when the collision is inelastic with e = 0.6.
a) 2.5
b) 2.00
c) 3.5
d) 3.1
Explanation:Velocity during elastic collision is given by
m1u1 + m2u2/(m1+ m2) = v
substituting the values we get
V = 2.5 m/s
v2 = 2(1+e)V – eu2
v2 = 3.1 m/s.
6. A sphere of mass 25 Kg is moving at a speed of 1.5 m/s undergoes collision with another sphere of mass 50 Kg moving at 3m/s in the same direction, find the velocity of 50 Kg mass in m/s after collision when the collision is inelastic with e = 0.6.
a) 2.2
b) 2.00
c) 3.5
d) 3.1
Explanation: Velocity during elastic collision is given by
m1u1 + m2u2/(m1+ m2) = v
substituting the values we get
V = 2.5 m/s
v1 = 2(1+e)V – eu1
v1 = 2.2 m/s.
7. Which of the following cases momentum is conserved?
a) Perfectly elastic collision
b) Inelastic collision with 0<e<1
c) Perfectly inelastic collision
d) Momentum is always conserved
Explanation: When the net external force acting on the body is 0, the linear momentum is always conserved no matter the type of collision
8. Which of the following cases Kinetic energy is conserved?
a) Perfectly elastic collision
b) Inelastic collision with 0<e<1
c) Perfectly inelastic collision
d) Momentum is always conserved
Explanation: When the net external force acting on the body is 0, the linear momentum is always conserved no matter the type of collision, however in only completely elastic collisions the kinetic energy of the system remains conserved.
9. The periodic time (tp) is given by
a) ω / 2 π
b) 2 π / ω
c) 2 π × ω
d) π/ω
Explanation: Periodic time is the time taken for one complete revolution of the particle.
Periodic time, tp = 2 π/ω seconds.
10. The velocity of a particle moving with simple harmonic motion is . . . . at the mean position.
a) Zero
b) minimum
c) maximum
d) none of the mentioned
Explanation: At mean the value of x = 0. Therefore, it is maximum at mean position.
Vmax = ω.r.