Question

Consider an automobile moving at v mph that skids d feet after its brakes lock. Calculate how far it would skid if it was moving at 2v and the brakes were locked.

Answer 1

Answer:

same retarding force so same acceleration

x = Vi t - (1/2) a t^2

v = Vi - a t

so for final v = 0

t = Vi/a

x = Vi^2/a - (1/2)Vi^2/a = Vi^2/a

if Vi new =2 Vi

then

x = 4 Vi^2/a

4 times as far

Answer 2

Consider an automobile moving at v mph that skids d feet after its brakes lock. Calculate how far it would skid if it was moving at 2v and the brakes were locked

same retarding force so same acceleration
x = Vi t - (1/2) a t^2
v = Vi - a t
so for final v = 0
t = Vi/a
x = Vi^2/a - (1/2)Vi^2/a = Vi^2/a
if Vi new =2 Vi
then
x = 4 Vi^2/a
4 times as far