Question

A car traveling at 20m/s when the driver sees a child standing in the road. He takes 0.80 seconds to react,then steps on the brakes and slows at 7.0 m/s^2. How far does the car go before it stops ?​

Answer 1

Answer:

44.6m

Explanation:

d = Vo*t + (Vf^2-Vo^2)/2a.

d = 20*0.8 + 0-(20)^2 / -14 = 44.6 m.

Answer 2

Given,

initial velocity (u) = 20 m/s

final velocity(v) = 0 m/s

Acceleration (a) = -7 m/s²

v² = u² + 2aS

where,

s is the distance travelled after brake

putting the values,

0 = 20² + 2(-7)S

-14S = -400

S = 400/14

= 28.57

so,

distance travelled = 28.57 m