Question

A traffic-safety engineer is designing a deceleration lane. She is basing the length of this lane on the distance needed to slow down from 126 km/h to 65 km/h in 8.0 s. How long will the deceleration lane be?

3.8 x 10² m

2.1 x 10² m

7.6 x 10² m

4.2 x 10² m

Answer 1

$a=\frac{v_0-v}t,$

$s=v_0t-\frac{at^2}2=\frac{(v_0+v)t}2,$

$s=\frac{(126+65)\cdot 8}{2\cdot 3.6}=764~m.$