JEE Main 2026 — Motion In One Dimension Question with Solution

Velocity of car A, $v_A=100$ km/h

Velocity of car B, $v_B=80$ km/h

Velocity of the stone relative to car B is $v$. The velocity of the stone relative to the ground is $v_S=v_B+v=80+v$.

The velocity of the stone relative to car A is $v_{S/A}=v_S-v_A=(80+v)-100=v-20$.

The stone hits car A with a relative speed of $5$ m/s. Converting this speed to km/h:

$v_{S/A}=5\times \frac{18}{5}=18$ km/h

Equating the relative speeds:

$v-20=18\Rightarrow v=38$ km/h

Answer: $38$