Question

A racing car moving at 126km/h is brought to rest in 5sec on applying brake. Find the retardation produced and the distance travelled by car before it comes to rest

Answer 1

v=126km/h =>35m/s

t=5sec

a=?

v=u+at

35=0+a*5

A =-7m/s²(retardation)

s=ut+½at²

=0*5+½*7*5²

½*7*25

=175/2km

Answer 2

given that:

initial velocity(u)=126km/h

change into m/s=126×5/18=35m/s

final velocity(v)=0m/s

retardation(acceleration) =?

time=5sec

distance covered by car=?

retardation=v-u/t = 0-35/5 =-7m/s2

retardation = -7 m/s2

find distance,

s=ut+1/2at2

s=35×5+1/2(-7)(5×5)

s=175+1/2(-175)

s=175-175/2

taking LCM

s= 350-175/2 = 175/2 = 87.5m

distance covered by car = 87.7m