Question

a bus decreases its speed from 180km/hr to 90km/hr in 5s . find the accerleration of the bus

Answer 1

Your answer is --

Since, a bus decreases its speed from 180km/hr to 90km/hr in 5s

such that ,
it's initial velocity u = 180km/h or 50m/s

final velocity v = 90km/h or 25m/s

also given, time period t = 5sec

Now, according to formula

a = v-u/t

=> a = 25-50/5

=> a = -25/5

=> a = -5m/s^2

Hence, acceleration of bus is -5m/s^2 ,
minus sign show that bus deaccelerated


【 Hope it helps you 】

Answer 2

v=90km/h = 5/18*90 =25m/s
u=180km/h= 5/18*180 =50m/s
t=5 second

                         v-u
                   a= -------
                           t
                         25-50
                  a= -----------
                             5
                            -25
                  a= ------------
                              5
                  a= -5m/s