Module 4 Challenge Problem 5 :
When I solve for t , I get ~2.1s.
My approach is:
v bus = a * t
x person = v person * t = a * t^2
x bus = x0 bus + 1/2 a * t^2 = a * t^2
x0 bus = 1/2 a * t^2
2 = 1/2 * 0.9 * t^2
t = 2.1
What am I doing wrong?

Question

Module 4 Challenge Problem 5 :
When I solve for t , I get ~2.1s.
My approach is:
v bus = a * t
x person = v person * t = a * t^2 
x bus = x0 bus + 1/2 a * t^2 = a * t^2
x0 bus = 1/2 a * t^2
2 = 1/2 * 0.9 * t^2
t = 2.1
What am I doing wrong?

anonymous · Answer

When the bus is 20m from the person it starts to accelerate at .9m/s^2, so for Bus: x(t)= 1/2at^2 and plug in 20 for x(t) and .9 for a and solve for t => t=6.7 secs.