Q 11-02-060JEE MainJEE Main 2024 (6 Apr, Shift 1)Easy
A train starting from rest first accelerates uniformly up to a speed of $80\ \text{km/h}$ for time $t$, then it moves with a constant speed for time $3t$. The average speed of the train for this duration of journey will be (in km/h)
Answer: (D) $70$
Distance while accelerating: $\dfrac{80}{2}t = 40t$. Distance at constant speed: $80\times3t = 240t$.
$$v_{avg} = \frac{40t + 240t}{4t} = 70\ \text{km/h}$$
Solution by Sreeraj P, M.Sc Physics