A vechicle moving with a speed of 36 km/h sees a red light ahead dg applies brakes and stops after covering 10 m distances. If moving at a speed of 72 km/h then applying brakes it stops after covering 30 m distance. Assuming same reaction time and same deceleration in each case, the distance covered when brakes are applied on the vehicle when it is moving at 54 km/h is

Let, the time in which the vehicle keeps on moving with the same speed before brakes are actually applied, i.e., reaction time be t0. Then In first case u2 = 2a (x - x0)or 36×5182=2a10−10t0...(1)In second case, 72×5182=2a30−20t0....(2)Similarly, 54×5182=2as−15t0....(3)Dividing (1) by (2),to = (1/ 2) secDividing eq. (t) by eq. (g) and puttingt0 =1/2, we gets =18.75m