Question
Two objects, each of mass 1.5 kg, are moving in the same straight line but in opposite directions. The velocity of each object is 2.5 ms–1 before the collision during which they stick together. What will be the velocity of the combined object after collision?
Solution
Here,
Mass of two objects are equal but their motion is in opposite direction.
That is,
m1 = m2 = 1.5 kg
Initial velocity, u1 = 2.5 ms-1, u2 = -2.5 ms-1.
Let v be the velocity of the combined object after the collision.
By conservation momentum,
Total momenta after collision = Total momenta before collision
i.e., (m1 + m2) v = m1u1 + m2u2
(1.5 + 1.5)v = 1.5 x 2.5 + 1.5 x (-2.5)
3.0 v = 0
So, v = 0 ms-1
Hence, the objects will have zero velocity after collision.
