Question

A motorist is driving at 18.1 m/s when she sees that a traffic light 192 m...

A motorist is driving at 18.1 m/s when she sees that a traffic light 192 m ahead has just turned red. She knows that this light stays red for 14.6 s, and she wants to reach the light just as it turns green again. It takes her 0.9 s to step on the brakes and begin slowing. What is her speed as she reaches the light at the instant it turns green?

d= Vi(t)+ 1/2a (t2)

173.9=18.1(13.7) +1/2a (13.72) ---> 173.9= 247.97 +1/2a (187.69) --->

-74.07= 1/2a(187.69) ---> -0.3946= 1/2a(187.69) ---> a= -0.78928

Vf= 18.1+(-0.78928)(13.7) ---> Vf= 7.2869 m/s (wrong answer)

I have also tried these answers (7.29 m/s , 7.3m/s, 16mph, 9.93m/s)

I have tried solving this 2 different ways and it keeps saying the answer is wrong

Science   Physics   
0 0
Add a commentTranscribed image text
Next >

Homework Answers

Answer #1

Solution:

Given that

u = initial speed =18.1m/s

x = distance travelled = 192 m

t = total time = 14.6 s

The distance travelled by motorist in 0.9 s is

The distance left to travel

Time left

The motorist now apllies brake, hence

175.71=18.1 *13.7-0.5*a*13.72

The final speed

v=18.1-.769*13.7

Try this i hope it will help you.

0 0
Know the answer?
Your Answer:

Post as a guest

Your Name:

What's your source?

Earn Coins

Coins can be redeemed for fabulous gifts.

Log In

Sign Up

Not the answer you're looking for?
Ask your own homework help question
Similar Questions
A motorist is driving at 19.2 m/s when she sees that a traffic light 203 m...
A motorist is driving at 19.2 m/s when she sees that a traffic light 203 m ahead has just turned red. She knows that this light stays red for 14.5 s, and she wants to reach the light just as it turns green again. It takes her 1.1 s to step on the brakes and begin slowing. What is her speed as she reaches the light at the instant it turns green?
A car is traveling at 13.0 m/s, and the driver sees a traffic light turn red....
A car is traveling at 13.0 m/s, and the driver sees a traffic light turn red. After 0.590 s (the reaction time), the driver applies the brakes, and the car decelerates at 8.00 m/s2. What is the stopping distance of the car, as measured from the point where the driver first sees the red light?
Suppose a car is traveling at +22.6 m/s, and the driver sees a traffic light turn...
Suppose a car is traveling at +22.6 m/s, and the driver sees a traffic light turn red. After 0.494 s has elapsed (the reaction time), the driver applies the brakes, and the car decelerates at 8.00 m/s2. What is the stopping distance of the car, as measured from the point where the driver first notices the red light?
A person driving her car at 53.0 km/hr approaches an intersection just as the traffic light...
A person driving her car at 53.0 km/hr approaches an intersection just as the traffic light turns yellow (see figure below). She knows that the yellow light lasts only 1.60 s before turning to red, and she is a distance D = 33.0 m away from the near side of the intersection. If she decides to stop, how far from the intersection will she come to a stop? The intersection is W =16.0 m wide. Her car's maximum deceleration is...
Paul is driving south down Pembina highway at a constant speed of 20 m/s. He sees...
Paul is driving south down Pembina highway at a constant speed of 20 m/s. He sees a truck in one of the north-bound lanes. The truck is initially stopped at the next traffic light, which is 500 m away. At this point, the light turns green and the truck starts accelerating northwards (towards Paul) at a constant acceleration of 1.2 m/s2. At what distance from the position where Paul first saw the truck, do they pass each other?
Two cars start from rest at a red stop light. When the light turns green, both...
Two cars start from rest at a red stop light. When the light turns green, both cars accelerate forward. The blue car accelerates uniformly at a rate of 3.3 m/s2 for 3.9 seconds. It then continues at a constant speed for 13.7 seconds, before applying the brakes such that the car’s speed decreases uniformly coming to rest 219.99 meters from where it started. The yellow car accelerates uniformly for the entire distance, finally catching the blue car just as the...
1) A speedboat increases its speed uniformly from vi = 20.0 m/s to vf = 36.0...
1) A speedboat increases its speed uniformly from vi = 20.0 m/s to vf = 36.0 m/s in a distance of Δx = 2.40 ✕ 102 m. (a) Draw a coordinate system for this situation and label the relevant quantities, including vectors. (b) For the given information, what single equation is most appropriate for finding the acceleration? vf = vi + at a = vf − vi tf − ti Δx = vit + 1 2 at2 vf2 = vi2...
Two cars start from rest at a red stop light. When the light turns green, both...
Two cars start from rest at a red stop light. When the light turns green, both cars accelerate forward. The blue car accelerates uniformly at a rate of 5.1 m/s2 for 4.3 seconds. It then continues at a constant speed for 11.9 seconds, before applying the brakes such that the car’s speed decreases uniformly coming to rest 361.87 meters from where it started. The yellow car accelerates uniformly for the entire distance, finally catching the blue car just as the...
1) A car is stopped for a traffic signal. When the light turns green, the car...
1) A car is stopped for a traffic signal. When the light turns green, the car accelerates, increasing its speed from 0 to 4.90 m/s in 0.834 s. (a) What is the magnitude of the linear impulse experienced by a 74.0-kg passenger in the car during the time the car accelerates? (b) What is the magnitude of the average total force experienced by a 74.0-kg passenger in the car during the time the car accelerates? 2) A 67-kg fisherman in...
Speedy Sue, driving at 34.0 m/s, enters a one-lane tunnel. She then observes a slow-moving van...
Speedy Sue, driving at 34.0 m/s, enters a one-lane tunnel. She then observes a slow-moving van 170 m ahead traveling with velocity 5.10 m/s. Sue applies her brakes but can accelerate only at ?2.00 m/s2 because the road is wet. Will there be a collision? Question 1: Yes or No If yes, determine how far into the tunnel and at what time the collision occurs. If no, determine the distance of closest approach between Sue's car and the van, and...
ADVERTISEMENT
Need Online Homework Help?

Get Answers For Free
Most questions answered within 1 hours.

Ask a Question
ADVERTISEMENT