Question

a bus is travelling at a speed of 72 km per hour the brakes are applied so as to produce a uniform retardation of 1.2 ms^-2. find the distance it travel after applying brakes so that it completely stops?​

Answer 1

Here,

u = 72 km/hr

             = 72 *5/18  m/s

             = 20 m/s

       

v = 0 m/s

a = -1.2 m/s^2 .           (Since it is retardation, so the acceleration will be -ve)

we know, a = v-u/t

so,   -1.2 m/s^2 = -20 ms^1/ t

    t = 20/1.2 s = 16.6 s

Now, we know,  

s= ut + 1/2 at^2

Therefore,

s = {(20 * 16.6) + 1/2 * (-1.2) * 16.6^2} m

  =332 + 165.336 m

   = 497.336 m