Question

A car is stopped at the traffic light. It then travels along a straight road so that its distance from the light is given by 𝑥(𝑡) = 𝑏𝑡2 − 𝑐𝑡3 where b=2.40 m/s2 and c=0.120 m/s3.

a) Calculate the average velocity of the car for the time interval t=0 to t=10.0 s.

b) Calculate the instantaneous velocity of the car at t=0 and t=10.0s

c) How long after starting again from rest is the car again at rest.

Answer 1

a)

$v_a=\frac x{\Delta t}=-20~\frac ms,$

b)

$v_i=2bt-3ct^2,$

$v_i(0)=0~\frac ms,$

$v_i(10)=12~\frac ms,$

c)

$t=\frac bc=20~s.$