Virtual Lab: Stopping Distance of a Car
Question: How can we determine the deceleration rate of a virtual car? How does reaction time affect the stopping distance of a car?

Go to this website: http://higheredbcs.wiley.com/legacy/college/halliday/0471320005/simulations6e/index.htm?newwindow=true and on the left side of the screen select “Stopping Distance of a Car”

Introduction: In this virtual experiment, a yellow sports car is coming to a stop from some initial velocity. On the left of the screen below the car you see a position vs. time and velocity vs. time graph of the motion. On the right of the screen below the car you are given lots of information about the car’s motion: time, distance covered, speed, distance traveled before braking, distance traveled after braking, and total stopping distance. Follow the instructions for the lab and answer questions as you proceed.

Instructions: 1. Load up the Java Lab from the website shown above. 2. On the left side of the screen select “Stopping Distance of a Car” 3. Before you start recording data for the lab, “play” around with the buttons at the bottom of the screen and see what they do. (Play, pause, reset, step back, step forward.) 4. When you feel comfortable, hit the “clear trace” button and go on to procedure 1.

Procedure-Part 1

Reset/clear trace and have the initial speed is set at 80 km/hr, the reaction time is 0.10 s, and the coefficient of friction is equal to 1.00. Answer the questions below PRIOR to running the simulation:

Analysis-Part 1

1. Convert 80 km/hr into m/s. (The graphs are in meters and seconds!) Show math.

1 hr = 3600 sec

1 km = 1000 m

80 km 1000 m 1 hr

------ × ------ × -------- = 22.2222 meters per second hr 1 km 3600 sec

2. Where do you see this speed in m/s confirmed on your screen? Right hand side on the speed button.

3. If the reaction time is 0.10 s, how far will the car travel before hitting the brakes? Show math. 0.10s *22.22 m/s = 2.22 m/s

4. Where do you see this distance you just calculated confirmed on your screen? The distance traveled before breaking line on the right hand side.

5. If the ultimate goal of the car is to come to a stop and they tell you the “distance traveled after braking”, can you calculate the deceleration rate of the car? Show math.

a = 0−802 10 = −6400 10 = - 640 m/s2

Procedure-Part 2

Now with the initial speed set at 80 km/hr, the reaction time at 0.10 s, and the coefficient of friction equal to 1.00, run the simulation and answer the questions below:

Analysis-Part 2

6. Looking at the position vs. time graph, describe the motion of the yellow car. The car is gradually coming to a stop in the 2.4 seconds it takes for it to stop. It evens out its position as it comes closer to completing its stop.

7. Looking at the velocity vs. time graph, describe the motion of the yellow car. The yellow car begins to slow down within the 27.41 m covered.

8. What is the slope of the velocity vs. time graph? Show math. 9.48-16.83 = -9.8 m/s/s 1.40-.65

9. What does slope represent on a velocity vs. time graph? It represents the negative velocity and the time it takes for the car to actually stop.

10. Make a screenshot of your entire screen and paste it on a word processing document that you can add to as this lab proceeds on. (Use the “Print Screen” button to copy your screen and the Paint program to cut out only the portion you want to copy.) All of the graphs you make for this lab should be able to fit on one piece of paper.

Procedure-Part 3

Reset/clear trace and have the initial speed is set at 100 km/hr, the reaction time is 0.10 s, and the coefficient of friction is equal to 1.00. Run the simulation and answer the questions below:

Analysis-Part 3

11. Convert 100 km/hr into m/s. (The graphs are in meters and seconds!) Show math.

1 hr = 3600 sec

1 km = 1000 m

100 km 1000 m 1 hr

------ × ------ × -------- = 27.778 meters per second hr 1 km 3600 sec

12. If the reaction time is 0.10 s, how far will the car travel before hitting the brakes? Show math. .10*27.778m/s=2.7778 m/s

13. If the ultimate goal of the car is to come to a stop and they tell you the “distance traveled after braking”, can you calculate the deceleration rate of the car? Show math. a = 0−1002 10 = −10000 10 = - 1000 m/s2

14. What is the slope of the velocity vs. time graph when you run the simulation? Show math. 17.49-8.67 = -9.8 m/s/s 1.15-2.05

15. Make a screenshot of your entire screen and paste it on a word processing document that you can add to as this lab proceeds on. (Use the “Print Screen” button to copy your screen and the Paint program to cut out only the portion you want to copy.) All of the graphs you make for this lab should be able to fit on one piece of paper.

Procedure-Part 4

Reset/clear trace and have the initial speed is set at any value except 80 or 100, the reaction time is 0.10 s, and the coefficient of friction is equal to 1.00. Run the simulation and answer the questions below: (60)

Analysis-Part 4

16. Convert your selected velocity from km/hr into m/s. (The graphs are in meters and seconds!) Show math.

1 hr = 3600 sec

1 km = 1000 m

60 km 1000 m 1 hr

------ × ------ × -------- = 16.667 meters per second hr 1 km 3600 sec

17. If the reaction time is 0.10 s, how far will the car travel before hitting the brakes? Show math. .10*16.667= 1.6667 m/s

18. If the ultimate goal of the car is to come to a stop and they tell you the “distance traveled after braking”, can you calculate the deceleration rate of the car? Show math. a = 0−602 10 = −3600 10 = - 360 m/s2

19. What is the slope of the velocity vs. time graph when you run the simulation? Show math. 15.20-5.40 = -9.8 .25-1.25

20. You now have calculated the acceleration of the yellow car three times (analysis questions 5, 13, and 18). Please calculate the average deceleration rate of the car (show math): -640+-1000+-360 = 666.67 m/s 3

21. Make a screenshot of your entire screen and paste it on a word processing document that you can add to as this lab proceeds on. (Use the “Print Screen” button to copy your screen and the Paint program to cut out only the portion you want to copy.) All of the graphs you make for this lab should be able to fit on one piece of paper.

Procedure-Part 5

Hit “Reset” and “Clear Trace”. Using the slider under the velocity, change the velocity back to 80 km/hr and the reaction time to 0.50 s. Hit the “Play” button, watch what happens, and answer the questions in the next section.

Analysis-Part 5

22. If the reaction time is 0.50 s, how far will the car travel before hitting the brakes? Show math. .50*22.22=11.11 m/s

23. If the ultimate goal of the car is to come to a stop and they tell you the “distance traveled after braking”, can you calculate the deceleration rate of the car? Show math. a = 0−802 50 = −6400 50 = - 128 m/s2

24. Did the deceleration rate change? Yes the deceleration rate changed. It got much smaller/shorter.

25. Now what is the total stopping distance, and how does this compare to the total distance traveled from part 1? The total stopping distance is 36.30 m. It is larger than the stopping distance traveled in part 1.

26. Make a screenshot of your entire screen and paste it on a word processing document that you can add to as this lab proceeds on. (Use the “Print Screen” button to copy your screen and the Paint program to cut out only the portion you want to copy.) All of the graphs you make for this lab should be able to fit on one piece of paper.

Conclusion-Answer the questions found under the title for this lab. Use complete sentences!

To find the deceleration rate of a virtual car is the negative of the speed squared then divided by the reaction time in seconds. The reaction time affects the stopping distance of a car dramatically. With a faster reaction time the car will stop quicker. With a slow reaction time the car will take longer to come to a complete stop.