Question

Exercise 2.7 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 = 2.60 m/s2 and c = 0.130 m/s3

Answer 1

The solution is:

x(t) = 3*t^2 - 0.130*t^3
v(t) = x'(t) = 6*t - 0.360*t^2

v(5) = 6*5 - 0.360*5^2 = 21 m/s
v(10) = 6*10 - 0.360*10^2 = 24 m/s

set v(t) = 0 and solve for t
0 = 6*t - 0.360t^2
0 = t*(6-0.360*t)
6-0.360*t = 0
t = 6/.360 = 16.7 s