Question

Two objects of masses 100 g and 200 g are
moving along the same line and direction with
velocities of 2 ms-1 and 1 m s- respectively.
They collide and after the collision, the first
object moves at a velocity of 1.67 ms!
Determine the velocity of second object.​

Answer 1

Explanation:

Before Collision After collision

A B A B

100 g 200g → 100g 200g

2m/s 1m/s v=? 1.67ms

−1

Let the 100 g and 200 g objects be A and B as shown in above figure.

Initial momentum of A=

1000

100

×2=0.2kgms

−1

Initial momentum of B=

1000

200

×1=0.2kgms

−1

∴ Total momentum of A and B before collision

=0.2+0.2=0.4kgms

−1

Let the velocity of A after collision =v

∴ Momentum of A after collision =

1000

100

×v=0.1v

Also, momentum of B after collision

=

1000

200

×1.67=0.334kgms

−1

∴ Total momentum of A and B after collision

=0.1×v+0.334

Using the law of conservation of momentum, momentum of A and B after collision = momentum of A and B before collision

0.1×v+0.334=0.4

0.1×v=0.4−0.334

⇒v=

0.1

0.066

=0.66ms

−1