Question

A motorist is traveling at 25m/s. He is 100 m from a stop light when he sees it turns yellow. His reaction time, before stepping on the brake is 0.50 ses
a. What is the distance traveled during the reaction time?
b. What is the velocity of the motorist at the end of his reaction time?
c. What steady deceleration while braking will bring him to a stop right at the light?

Answer 1

Answer

given,

speed of motorist = 25 m/s

distance = 100 m

time to apply break = 0.5 s

a) distance traveled during the reaction time

   D = s x t

   D = 25 x 0.5

   D = 12.5 m

b) the velocity of the motorist at the end of the reaction time is equal to 0 m/s

c) using equation of motion

  v² = u² + 2 a s

    v = 0 m/s

    u = 25 m/s

  0² = 25² + 2 x a x 100

  $a =- \dfrac{625}{200}$

      a = -3.125 m/s²