Question

Two objects, each of mass $1.5\mathrm{kg}$, are moving in the same straight line but in opposite directions. The velocity of each object is $2.5\mathrm{m}{\mathrm{s}}^{-1}$ before the collision during which they stick together. What will be the velocity of the combined object after collision?

Answer 1

Step 1: Given data

$m_1=m_2=1.5\mathrm{kg},u_1=2.5{\mathrm{ms}}^{-1}$
${\mathrm{u}}_2=-2.5{\mathrm{ms}}^{-1}$

Step 2: Calculations.

If v is the velocity of the combined object after the collision. By conservation of momentum,
Total momenta after collision = Total momenta before the collision.
$\left(m_1+m_2\right)v=m_1{u}_1+m_2{u}_2$
$(1.5+1.5)v=1.5\times 2.5+1.5\times (-2.5)$
$3.0v=0$
or $v=0{\mathrm{ms}}^{-1}$

Hence, $v=0{\mathrm{ms}}^{-1}$ will be the velocity of the combined object after the collision.