A car driving at 50.0 km/hr approaches an intersection right when the light star

Question

A car driving at 50.0 km/hr approaches an intersection right when the light starts to change to yellow. The yellow light only lasts for 1.50 sec before it goes to red. The distance from the car to the start of the intersection is 34.0 meters.(A) If the car wants to stop how far from the intersection will it come to a stop? given that the intersection is 16.0 meters wide, and the car's max deceleration is -6.40 m/s^2. Please ignor the length of the car and reaction time of the person. (B) If the car can accelerate from 50.0 km/hr to 65.0 km/hr in 6.50s how far from the intersection will the car be when the light turns red?

Please show all your work...*** Also the answer for part A is NOT 15.07 meters. Thank you.

Explanation / Answer

Here ,

initial speed of car , u = 50 km/hr

u = 13.9 m/s

time , t = 1.50 s

A) Using third equation of motion

for finding the stopping distance of the car ,

v^2 - u^2 = -2*a*d

0 - 13.9^2 = -2 * 6.40 * d

d = 15.1 m

distance from start of intersection = 34- 15.1

distance from start of intersection = 18.9 m

the distance from start of intersection is 18.9 m

B)

Here , final speed , v = 65 km/h

v = 18.1 m/s

acceleration , a = (v - u)/t

a = (18.1 - 13.9)/6.50

a = 0.639 m/s^2

Now, distance travelled by car ,

d = 13.9 * 1.5 + 0.5 * 0.639 * 1.5^2

d = 21.6 m

distance from intersection = 34 - 21.6

distance from intersection = 21.4 m

the distance of car from intersection when the light turns red is 21.4 m

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.