Name: CM! Date: 7-Fe Phys 205.004 Spring 2018 Quiz #2 t; (2),,-my + vt +; (3) -f

Question

Name: CM! Date: 7-Fe Phys 205.004 Spring 2018 Quiz #2 t; (2),,-my + vt +; (3) -f + 2a (y-r); st of Eq astruction: Sh uations: (1) uf=vita ow your steps. To avoid round-off error, compute the numbers at the very e your solution You're approaching an intersection at 50 km/h. You see the light turn yellow when you are 35 m from the intersection. Assume a reaction time of 0.6 s before braking begins and a braking acceleration of -3.0m/s2. (a) Will you be able to stop before the intersection? (b) The yellow light stays on for 3.4s before turning red. If you continue at 50 km/i without braking, will you make it through the 9.5-m-wide intersection before the light turns red?

Explanation / Answer

(A) v0 = 50 km/h = 50 x 1000 m / 3600s = 13.9 m/s

distance travelled during reaction time.

d1 = vt = 13.9 x 0.6 = 8.33 m

after that,

vf^2 - vi^2 =2 a d

0^2 - 13.9^2 = 2(-3)(d2)

d2 = 32.15 m

total distance d = d1 + d2 = 40.5 m that is more than 35

Ans: No  

(b) d = v t = 13.9 x 3.4 = 47.22 m

total distance have to travel to cross,

= 35 + 9.5

= 44.5

yes, You will be able to cross.

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