Question

You are driving a car, traveling at a constant velocity of 25m/s, when you see a child suddenly run into the road. It takes 0.45s for you to react and apply the brakes. As a result, the car slows with a steady acceleration of 8.5m/s2 and comes to a stop. What is the total distance that the car moves before it stops?

Answer 1

Temos que contar a distancia que ele percorreu com o tempo de reação mais a distancia que andou até parar:

Space para o tempo de reação:

25 . 0,45 = 11,25m

Space para parar:

v^2 = v0^2 + 2.a.S

v = 0

v0 = 25m/s

a = -8,5m\s^2

s = ?

0^2 =(25)^2 - 2 .(-8,5).S

625 = 17.S

S = 625/17 = 36,7m

Logo, a distancia total foi de:

36,7 + 11,25 = 48m

Resposta: 48m