Engineering Questions with Answers - Multiple Choice Questions

# Machine Kinematics – Loss of Kinetic Energy During Elastic Impact

1 - Question

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 loss of kinetic energy when the collision is inelastic.
a) 18.75 N-m
b) 19.75 N-m
c) 17.75 N-m
d) 16.75 N-m
Explanation: Loss of kinetic energy during inelastic collision is given by m1m2/(2(m1+ m2) (u12 – u22) substituting the values we get El = 18.75 N-m.

2 - Question

The coefficient of restitution is 0 for a completely inelastic collision.
a) True
b) False
Explanation: For a completely inelastic collision the bodies stick to each other after collision, hence there is no relative velocity after collision therefore the coefficient of restitution is 0.

3 - Question

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 loss of kinetic energy when the collision is inelastic with e = 0.6.
a) 18.75 N-m
b) 12.00 N-m
c) 13.75 N-m
d) 12.75 N-m
Explanation: Loss of kinetic energy during inelastic collision with coefficient of restitution is given by m1m2/(2(m1+ m2) (u12 – u22)(1-e2)) substituting the values we get El = 12 N-m.

4 - Question

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 common velocity in m/s after collision when the collision is completely inelastic.
a) 2.5
b) 9.75
c) 7.25
d) 6.75
Explanation: Common velocity during inelastic collision is given by m1u1 + m2u2/(m1+ m2) = v substituting the values we get V = 2.5 m/s

5 - Question

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 elastic.
a) 2.5
b) 2.00
c) 7.25
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 v1 = 2V – u1 v1 = 2m/s

6 - Question

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.

7 - Question

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.

8 - Question

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.

9 - Question

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

10 - Question

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.

11 - Question

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.

12 - Question

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.

13 - Question

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