1. vf2 = vi2 + 2a ∆x vf2 - vi2 2a (0 m/s)2 – (26.8 m/s)2 = ∆x 2(-3m/s2)
- 6
120 m
You are driving at 26.8 m/s approaching a traffic light. It turns yellow. You slow down at a rate of -3m/s2
How far do you travel until you stop?
= ∆x
= ∆x
Given:
vi = 26.8m/s
a = -3 m/s2
vf = 0 m/s
∆x =?
= ∆x
= ∆x

2. vf = vi + at vf - vi a (0 m/s) – (26.8 m/s) = t -3m/s2 9 s = t = t
You are driving at 26.8 m/s approaching a traffic light. It turns yellow. You slow down at a rate of -3m/s2
How much time passes?
= t
= t
Given:
vi = 26.8m/s
a = -3 m/s2
vf = 0 m/s
t =?

3. You are driving at 26. 8 m/s approaching a traffic light
You are driving at 26.8 m/s approaching a traffic light. It turns yellow. You slow down at a rate of -3m/s2
If you are 125 m away from the light when you hit the brakes, will you stop ahead of the light, precisely at the light, or will you go beyond the light?
You will stop 5 m before the light.
125 m – your stopping distance
125 m – 120 m = 5 m
120 meters
5 m
125 meters

4. You are driving at 26. 8 m/s approaching a traffic light
You are driving at 26.8 m/s approaching a traffic light. It turns yellow. You slow down at a rate of -3m/s2
If the light is yellow for 2 seconds before it turns red, did you make the correct decision to slow down? Why or why not?
Yes, you made the correct decision.
It took 9 seconds to stop and the light turned from yellow to red after 2 seconds. Therefore the light was already red for 7 seconds by the time you stopped
120 meters
5 m
125 meters

5. = a = a Given: vi = 26.8m/s a = ? = a vf = ? ∆x = 125 m ∆t = 2 s
∆x = vit + ½at2
∆x - vit
½(t2)
125 m – (26.8 m/s)(2 s)
½ (2 s)2
71.4 2
35.7 m/s2 = a
You are driving at 26.8 m/s approaching a traffic light. It turns yellow. You slow down at a rate of -3m/s2
Can you figure out what you would have to do to ‘make the light’, i.e. get through it in two seconds and being 125 m away?
= a
= a
Given:
vi = 26.8m/s
a = ?
vf = ?
∆x = 125 m
∆t = 2 s
= a

6. CRAZY Given: vi = 26.8m/s a = 35.7 m/s2 vf = ? ∆x = 125 m ∆t = 2 s
vf2 = vi2 + 2a ∆x
vf2 = (26.8 m/s)2 + 2(35.7 m/s2)(125m)
vf2 = 9643
vf =
vf = 98 m/s or 216 mph
You are driving at 26.8 m/s approaching a traffic light. It turns yellow. You slow down at a rate of -3m/s2
Can you figure out what you would have to do to ‘make the light’, i.e. get through it in two seconds and being 125 m away?
Given:
vi = 26.8m/s
a = 35.7 m/s2
vf = ?
∆x = 125 m
∆t = 2 s
CRAZY