Science & Mathematics » Physics » A car is stopped at a traffic light. It then travels along a straight road so that its distance from the light is given by?

A car is stopped at a 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
. What is the instantaneous speed of the car at t = 20.0 sec ?
A) −48 m/s
B) 0
C) 48 m/s
D) 96 m/s

I know the answer is A, but can someone explain to me why

1 Answers1