Two objects, each of mass 1.5 kg,

Solution:

Let the objects be $\mathrm{A}$ and $\mathrm{B}$ moving from opposite directions in the same straight line.

$\therefore$ Initial momentum of $\mathrm{A}=\mathrm{m} \times \mathrm{v}$

$=1.5 \times 2.5=3.75 \mathrm{~kg} \mathrm{~ms}^{-1}$

Also, initial momentum of B

$=\mathrm{m} \times \mathrm{v}=1.5 \times(-2.5)=-3.75 \mathrm{~kg} \mathrm{~ms}^{-1}$

If v is the velocity of the objects after collision, then final momentum after collision = 3 × v

Using the law of conservation of momentum, final momentum of A and B = initial

momentum of A + initial momentum of B

or $3 \times v=3.75-3.75$

or $\quad 3 \times \mathrm{v}=0$ or $\mathrm{v}=\mathbf{0}$