Q 11-02-055JEE MainJEE Main 2024 (1 Feb, Shift 2)Easy
Train A is moving along two parallel rail tracks towards north with $72\ \text{km h}^{-1}$ and train B is moving towards south with speed $108\ \text{km h}^{-1}$. The velocity of train B with respect to A and the velocity of the ground with respect to B are (in $\text{m s}^{-1}$)
Answer: (C) $-50$ and $30$
Take north as positive: $v_A = 72\ \text{km h}^{-1} = 20\ \text{m s}^{-1}$, $v_B = -108\ \text{km h}^{-1} = -30\ \text{m s}^{-1}$.
$$v_{BA} = v_B - v_A = -30 - 20 = -50\ \text{m s}^{-1}$$
$$v_{\text{ground},B} = 0 - v_B = 30\ \text{m s}^{-1}$$
Solution by Sreeraj P, M.Sc Physics