Chapter 1: Driving the Roads
What is Physics Lab:
Station 1:

1. the further back you pull the car, the faster it goes
2. the car moves when you pull it back
3. race car drivers & children
4. to measure speed and time

Station 2:

1. When its connected to the rod, the spring takes the mass of the rods by moving up and down.
2. It weighs things
3. Scientists & construction workers
4. Moves heavy things

Station 3:

1. the spring keeps the weight from hitting the ground
2. The spring bounces up and down
3. Scientists
4. Keep the weight off the ground

Station 4:

1. the hair spray shows the lazer through the thick glass
2. it shows where the lazer would go through
3. thieves
4. to help people break into places and see the lazers and know where not to step

Station 5:

1. This object balances the things tied to the ends of it.
2. It moves to the heavier weighted thing
3. Anybody
4. A wind chime

Station 6:

1. It holds liquids
2. It keeps the liquid from going somewhere.
3. Anybody
4. This cup can be used to drink out of and it could be used for decoration

Section 1:

Learning Objectives:

• Measure reaction time using one of two different methods
• Compare the different methods of measuring reaction time
• Compare the reaction times of your classmates
• Investigate how distractions affect reaction time

What do you see?

• 2 cars crashed and another car behind trying to stop
• a road
• mountains in the background
• the guy in the blue car is coming around a turn--fast

What do you think?

• the distance between the cars
• distractions--weather, phones
• speed
• car condition

Investigate:

Stop watches:

2:03/2:17=14 seconds
1:96/2:08= 14 seconds
2:65/2:75= 11 seconds

Yard stick:

13=.17
10=.14
12=.15

Comparison:

#1
A) They weren't the same but they were similar. They weren't the same because everyone has different reaction times.
B) The stop watches
#2
A) Fastest- .12
Slowest- .17
Average- .14
B) Yes, their reaction times will vary. However, they not vary to much because younger people will have a faster reaction time because they have faster reflexes.
Red/Green Distraction:
1. 22
2. Green
3. 31
4. 19
5. Green
- Your reaction time is delayed.
Red/Green Distraction with calculator:
1. 25
2. Green
3. 72
A) Compare Reaction Times:
1. 25, 13
2. Green, 10
3. 31, 12
B) 10 Distractions while driving:
talking on the phone
texting
changing radio
eating
putting on make-up
being tired
sneezing/coughing
fixing hair
looking at time
GPS

Homework: 9/11/11

In the three videos they tested whether it was just as dangerous to drive while talking on the phone as it is while driving drunk. In the first video the 2 mythbusters drove the course while they were not on the phone and sober. Both of them passed the driving test. However, when they were driving while on the phone they were distracted and could not focus. Instead of only being focused on the road, they were trying to multitask by answering the questions and paying attention to the road. The end result of the cell phone test was that both drivers had failed. When they tested the drunk driving, both drivers tried to focus, but in the end could not. At certain points in the road test they had done better than some of the other times. For example, when the female driver drove drunk she did better at the parallel parking than she did while she was on the phone and sober. The outcome of the drunk driving test was that both drivers had failed. In the end that mythbusters decided that driving while on the phone and drunk driving are equally bad.

Physics Talk & Checking Up:

- Everyone's reaction time varies. The better reaction time you have, the better you can respond to the situation
reaction time- the time it takes to respond to a situation
- You have a slower reaction time when you are distracted
Your reaction time in the car will be slower than it was during these tests
1. Distractions can affect your reaction time which can change how fast or slow your respond to the situations on the road.
2. Alcohol and drugs can significantly change someones reaction time.
3. Age, gender, fatigue, exercise, and attentiveness

Physics Plus:

#1

Time (s)	Distance
0.00	0
0.02	.196
0.04	.784
0.06	1.764

A) The chart in the book and my chart are the same.

#2

B) Right Hand/Index & Thumb- 5cm
Left Hand/Index & Thumb- 8cm
Right Hand/Middle & Thumb- 8cm

Notes: 9/15/11

What do you think now?

There are many factors that affect the time you need to react to an emergency while driving. Some of them are drugs, alcohol, age, gender, practice, fatigue, exercise, attentiveness, and personality.

Essential Questions

1. Reaction time is the time it takes to react to a situation.
2. Two students held stopwatches. They started them at the same time. One student stopped the stopwatch and the other student had to watch when the stopwatch was stopped. The difference between the times of the two students to stop was there reaction time.
3. Reaction time is a measure of change over time because as you get older the slower your reaction time is.
4. The better your reaction time is the more likely you are to avoid an accident.

Section 2:

Learning Objectives:

• Calibrate the length of a stride
• Measure a distance by pacing it off and by using a meter stick
• Identify sources of error
• Evaluate estimates of measurements as reasonable or unreasonable

What do you see?

• There is a person measuring a little girl's stride and a teenagers stride
• The teenager's stride is bigger than the little girl's
• They are in a school
• The ground is uneven

What do you think?

• yes, I think one student made a mistake because the numbers are different by 7 meters
• no. i do not think they made a mistake because it is only off by .01

Precision- How repeatable the measurements are
Accuracy- How close the measurement is to the true value

Investigate:

number of strides- 35
length of stride- 51
Total- 35*51=1,836
Meter Stick- 2,253 cm
Tape Measure- 2,261

Groups	Stride	Meter Stick	Tape Measure
1	2006	2253	2261
2	1100	1369	1370
3	900	1369	1370
4	867	1369	1370
5	1598	2253	2261
6	756	1369	1370

#5
A) No, because everyone's stride is different depending on how they they walk. The lowest number is 867 and the highest number is 2006.
B) People walk differently. Some people take big stems and some take small.
Height
long/short legs
C) Everyone would have to take the same length steps. If we did this method then everyone would have the same or similar strides.
#7
A) No, because they were measured from different distances.
B) Two of the distances were measured different from the others
C) Everyone would have to measure the same distances.
D) The groups would not get the same value however they would get around the same area.
E) No, they can't all agree exactly because people measure things differently.

A) No, we didn't have an errors.
B) We had no errors.

Physics Talk Summary:

• There is never an exact measurement, there will always be differences in measurements
• There are two different types of errors: random errors and systematic errors
• Random errors- errors that cannot be corrected by calculation
• Systematic errors- errors that are produced by using the wrong tools or using the tool incorrectly for measurement and can be corrected by calculation
• Precision- How repeatable the measurements are
• Accuracy- How close the measurement is to the true value
• You can have accuracy without precision and precision without accuracy

Checking Up:

1. A systematic error is an error that is produced by using the wrong tools or using the tool incorrectly for measurement and can be corrected by calculation. A random error is an error that cannot be corrected by calculation.
2. There will always be an uncertainty with a measurement because the measure could fall in between two whole numbers and a guess is made about the rest of the number.
3. The arrows would be all in different places and none near each other or where they are supposed to be.

Do Now: 9/22/11

1. 6.789, 6.784, 6.781- random error
2. Using inches to measure a length instead of cm- systematic error

Section 2: Notes

26.7cm +/- 0.1cm
5,000cm +/- 1,000cm
510cm +/- 10cm
10.250 +/- .001cm
with decimal go to the right
without the decimal to the left to the closest non zero number
2,000,000 +/- 1,000,000
2,000,000.00 +/- .01

Physics Plus

1. A) If the pool had an uncertainty of 10cm then the range in length could be from 49.90-50.10.
B) If it had an uncertainty of 1cm the range in length could be 49.99-50.01.
C) If it had an uncertainty of 1mm then the pool range could be 49.999 and 50.001
2. 50m/25s, 2m/s, 200cm/s
2cm/200cms= 1/100=.01s --- s=d/t, t=d/s
3. 1500/15=.60/x
9/1500= 1500x/1500
x= .006 min
x= .36s
4. yes, because there is always an uncertainty with measurements, the new pool could be .01 less than the previous pool that the old record holder swam in.

What do you think now?

1. yes, one of the student has made a mistake. They made a systematic error.
2. yes, one of them has mad e a mistake, however they made a random error which can be corrected.

Essential Questions

1. This is a systematic error. Systematic errors affect accuracy and random errors affect accuracy & precision.
2. Every measurement has some uncertainty whether it is less or more than what is said.
3. Because the actual number is around the number that is given.
4. You could get into a car accident and injure yourself or someone else.

Physics to Go

5. Pretty accurate
6. No
7. Yes
8a. You should go 5mph under the posted speed to make sure that you do not go over the speed limit.'

Section 3

Learning Objectives:

• Define and contrast average speed and instantaneous speed
• Use strobe photos, graphs, and an equation to describe speed
• Use a motion detector to measure speed
• Construct graphs of your motion
• Interpret distance- time graphs
• Calculate speed, distance, and time using the equation for average speed

What do you see?

• Three cars are getting in a car accident
• The cars on the other side of the road have separation between the two of them
• The blue car stopped short and the red car hit her and the yellow car was speeding and hit her

What do you think?

• A safe distance between two cars is length of another automobile per each mile per hour
• You decide what a safe following distance between two cars is that you make sure you have enough time to stop so you can avoid an accident-- speed, reaction time, weather, age of the car

Investigate

#1
A)

#2
A)
B) The 30 mph cars were closer together than the 45 mph cars.
C) You can decide how far apart to place the cars based on the picture of the 45 mph cars are drawn
#3
A) C is traveling the slowest, A is traveling the fastest
B) Yes, because the distance is the same between each car in each section
#4
A, B, C, D


E) The first graph was walking away from the motion sensor and over 3 seconds, it went from about 2.2 to .1. The second one while walking towards the motion sensor was also 3 seconds, and started at .1 and ended up at 2.2. The third graph was walking away from it at a normal speed then walking back very slowly which was like 11.4 seconds, and started at .1 then went to 3 then ended at .8. The fourth graph walking in both directions really fast was about 4.2 seconds, and started at .1 then went to 2.2, and back down to .6.
#5
A)
B) It was wrong
#6

A)

B) You can determine this because the first line would be the slower walking away because its a longer line and the dots are closer together, the second line would be the faster walking away because the line is shorter and the dots are father apart.
#7
A) Distance is 2.2
B) It took 4.9 seconds
D) If it went for 9.8 seconds, it would go 4.4 meters. We are going to assume that the speed of the walking stays the same.
#8
A) 60= d/ 0.5
d= 60* 0.5
d= 30s
B) 60= d/ 0.5
d= 60* 1.5
d= 90s
C) 50* 0.5, d= 25s
50* 1.5, d= 75s
D) 70* 0.5, d= 35s
70* 1.5, d= 105s
E) They should stay far behind because they would only have 20 seconds to stop if they came to close
D) 60/15= 4, 4 cars lengths behind

Physics Talk Summary

• speed- the distance traveled per unit time; speed is a scalar quantity, it has no direction
• constant speed- speed that does not change over a period of time
• average speed- the total distance traveled divided by the time it took to travel that distance
• when an object is moving at a slow speed, the distance between the objects is less than when the object is moving at a fast speed
• average speed= distance traveled/ time elapsed
• 
• instantaneous speed- the speed at a given moment
• velocity- the speed in a given direction
• Model 1: Strobe Photos
  • used to illustrate the velocity of an object by the distance between the object in each picture
• Model 2: Solving Equations
• Model 3: Distance vs Time Graphs
  • slope= rise/ run
  • avg speed= distance/ time
  • slope= average speed
• 
  • A) A person is at rest time
  • B)A person is traveling at slow speed. As time goes on there is a little change
  • C) A person is traveling at a fast speed
  • D) A person is in the opposite direction than the other graphs
  • E) A person is changing speed- slow to faster
• reaction distance- the distance that a vehicle travels in the time it takes the driver to react

Checking Up

1. The average speed is the total distance traveled divided by the time it took to travel that distance. Instantaneous speed is the speed at a given moment.
2. Speed is the distance traveled per unit time; speed is a scalar quantity, it has no direction. Velocity is the speed in a given direction.
3. A straight inclined line would represent a person walking away from the motion sensor at a constant speed.
4. If you have a short reaction time then you will have a much shorter reaction distance.

Physics Plus

v=d/t, 80/3= 27
Average speed is always total distance/ total time
#1

#2

#3
A) I estimate that the average speed will be 40.
B) The actual average speed is 18.75 mi/h

Speed	Distance	Time
50 mi/h	50 mi	1hr
25mi/h	50 mi	2hr
10 mi/h	50 mi	5hr

v= 150/8
v= 18.75 mi/h
#4
A) 800

What do you think now?

• A safe following distance should be something that you feel safe with so that your reaction distance will give you enough time to stop
• A safe following distance depends on the individuals reaction time, reaction distance, distractions, and your speed.

Physics to Go

#1
A) The cars are moving at a constant speed.
B) The first three cars are moving at a constant speed, then there is a break in between because they stopped moving and then they started up at a constant speed.
#2
A and B

#3
v=d/t, (v)(t)=d
(350)(20)=d
d= 7,000 ft
#4
A) Her average speed was 48mph
v=d/t, v=215/4.5
v= 48
B) No, because you don't have the instantaneous speed.
#5
d=5, t=.25, v=?
v=5/.25
v= 20mph
#6
A) The vehicle was going at a constant speed and then stopped
B) The vehicle was going in one direction at a constant speed, stopped and continued in the opposite direction at a slower speed than the beginning
C) The vehicle is going slow at a constant speed and then continues at a faster constant speed
D) The vehicle was going away from the sensor at a fast speed
#7
A) 55/13= 4.2
B) 35/13= 2.7
C) 55/22= 2.5
#8
A) They can test people's reaction distances which is the distance that a vehicle travels in the time it takes the driver to react
B) No, because on an interstate highway there are much more cars and in a rural area most of the time the driving will be traffic free.
#9
A) 70/3= 23.33
B) No
#10
A) 88*0.5= 44ft
B) 44/15= 2.9
about 3 car lengths
C) 44*0.5= 22ft, 22/15= 1.46
1 or 1.5 car lengths
D) 90*0.5= 45, 45/15= 3
about 3 car lengths
E) They all double
#11

Essential Questions

1. To say that the speed of a car is 40mph means that 40mph is the average speed of the car
2. You would find the average speed of a vehicle using the equation v=d/t
3.The strobe photo can show the dots at the same distance apart from each other. An equation can calculate the exact speed needed. The graph can show a slope of 20
4. If you have a fast reaction time then your reaction distance will be further away from the car in front, so that you can avoid accidents.

Section 4

Learning Objectives

• Measure a change in velocity (acceleration) of a cart on a ramp using a motion detector
• Construct graphs of the motion of a cart on a ramp
• Define acceleration using words and an equation
• Calculate speed, distance, and time using the equation for acceleration
• Interpret distance-time graphs for different types of motion

What do you see?

• The red car is speeding through an intersection
• The man and the dog are running to the sidewalk to get out of the way

What do you think?

• They will both start rolling at the same time
• The car will get to 30mph faster because there is less weight/people
• The car is going to cover more ground in the same amount of time that the bus would

Investigate

#5

Physics Talk

• acceleration- the change in velocity with respect to a change in time
• acceleration means "how fast the velocity changes", a vector quantity
• vector- a quantity that has both magnitude and direction
• ways to change your automobiles velocity
  • speed up (increasing the speed, or magnitude of velocity)
  • slow down (decrease speed, or magnitude of velocity)
  • turn (change the direction of the velocity)
• velocity changes as time elapses
• negative acceleration- a decrease in velocity with respect to time. The object can speed up (20 m/s to 30m/s) or slow down (-20m/s to -10m/s)
• positive acceleration- an increase in velocity with respect to time. The object can speed up (20 m/s to 30m/s) or slow down (-20m/s to -10m/s)
• vector quantity- involves both direction and size-- velocity is a vector quantity (34 mi/h, South)
• scalar quantity- a quantity that has size, but not direction-- speed is a scalar quantity (34 mi/h)
• 
  • shows the automobiles moving greater distances during each second of travel
• 
• tangent line- a straight line that touches a curve in only one point-- gives instantaneous speed at that point
• 
• 
  
• 

Checking Up

1. acceleration= change in velocity/ change in time
a= v/t
2. Acceleration is (m/s)/s or velocity is (km/h)/s
Velocity is m/s or km/h
Time is (s) seconds
3. A vector quantity involves both direction and size. A scalar quantity a quantity that has size, but not direction.
4.
5. Instantaneous speed

*Questions

1. Velocity is the slope of a d vs. t graph because v= d/t. Slope=rise/run=distance/time=acceleration
2. Acceleration is the slope of a v vs. t graph because v=d/t.
3. You need to use tangent lines to find instantaneous speed because the point can tell you the speed at that very moment and instantaneous speed is the speed at a given moment

Notes

Physics Plus

Homework

1. 1999.2 m
2. 3.125 km
3. 2.2 s
4. 2 seconds
5. 7721.4 m
6. 18.75 m
7. a. 29.65 m
b. 9.89 m/s
8. a. Not enough information
b. 19.3 m/s
9. 27 s
10. a. 2.5 seconds
b. 31.25 m
c. No
d. Know how to identify important information

Section 5

Learning Objectives

• Plan and carry out an experiment to relate braking distance to initial speed
• Determine braking distance
• Examine accelerated motion

What do you see?

• A car is driving down a road and a moose is in the middle of the road
• The car is stopping in order to avoid hitting the moose
• the car was going fast
• the car might have stopped short because of the smoke coming off of the tires and the back wheels are not on the road

What do you think?

• speed
• reaction time
• reaction distance
• road/weather conditions

Investigate

1.
A) Prediction Graph

B) I drew the graph this way because i thought that the car would continues at the same speed until it eventually slowed down
4.

Run	Measurement
1	3.2m
2	3m
3	3.5m
4	2.8m
5	2.6m
6	1.5m
7	2.5m

Slopes for graphs:
2) 1.75
3) 2
4) 1.2
5) 2.2
6) .75
7) 2

5.
B) A car with faster initial speed will have a longer braking distance because it is going faster and will take longer to slow down.
C) It is around the same thing
D) Most other groups had curvy graphs
E) After seeing other people graphs I feel good about ours even though they are a little different than other groups.

6. For the 6th run the slope was .75 and almost double .75 is 1.75 which was from run 2.
A) Doubling the speed affects the breaking distance because it will make the car have a longer breaking distance because it is going significantly faster.

7. For the 6th run the slope was .75. Double that speed is 2.25. The closest number that was had to that was 2 on run 3 and run 7.
A) Tripling the speed would make it even harder for the car to stop making the breaking distance even longer than doubling it.
B) The breaking distance would be 4 times longer if we made the speed 4 times faster.

Physics Talk

Checking Up

1. If a vehicle is traveling at a constant velocity and then comes to a sudden stop it has undergone a negative acceleration. It has gone under a negative acceleration because the car has stopped.
2. If a car is traveling at a fast speed then it will take the car a longer time to brake because the speed slowly has to become lower.
3. the term negative acceleration is used instead of deceleration because it is referring to the speed rather than the direction of the car.

Physics Plus

Physics to Go/Homework

Answers:
1. a=38
2. a=.048
3. d= 5148.82
4. d= -.79
5. Graph

Notes

Section 6

Learning Objectives

• Investigate the factors that affect the STOP and GO Zones at intersections with traffic lights
• Investigate the factors that result in an Overlap Zone or a Dilemma Zone at intersections with traffic lights
• Use a computer simulation to mathematically model the situations that can occur at an intersection with traffic lights

What do you see?

• Two cars are at an intersection
• The green car was speeding and went through a red light
• The red car was speeding and tried to stop before the red light

What do you think?

• Different speed limits will need different stopping distances
• Some people try to speed up during a yellow light and may go through a red
• Power outage makes intersection dangerous, people running lights

Investigate

3.
a. yes
b. yes, if Automobile A is in the go zone then Automobile B in front of it is
c. yes
d. No Automobile C is not in the go zone. If Automobile C goes through the intersection they will run a red light
4
a. yes
b. no, Automobile F is not in the stop zone it is on the go zone. If it decides to stop it might stop short causing an accident behind it.
c. Sketch
5.

Variable	Change	Predicted Affect	Actual Affect
ty	yellow light time increase decrease	bigger smaller	bigger smaller
tr	response time increase decrease	bigger smaller	bigger smaller
v	speed limit increase decrease	bigger smaller	bigger smaller
a	negative acceleration increase decrease	smaller bigger	bigger smaller
w	width of intersection increase decrease	bigger smaller	smaller bigger

6.
a. 53 meters
b. I will increase to 63 meters

c. yes, that would then make the GO zone bigger making it easier for more cars to make it through the yellow light
d. Changing the time of the yellow light would affect where and how big the STOP and GO zones are it would allow for more cars to go through the intersection.
7.
a. yes, if you increase the yellow light time the GO ZONE size increases as well
b. done on 5b
c. (B5*B4)+(B5^2)/ (2*B6)
d. All of the different elements such as yellow light time, speed, and width of intersection all affect each other when changed
e. They aren't in the equation because they do not have an affect on the GO ZONE.
8.

Variable	Change	Predicted Affect	Actual Affect
ty	yellow light time
tr	response time
v	speed limit
a	negative acceleration
w	width of intersection

9.
a. (vehicle speed*response time)+(vehicle speed^2)/ (2* negative acceleration)
(B5*B4)+(B5^2)/(2*B6)
STOP ZONE= (vt)+v^2/2a
b. They are not in the equation because they don't affect the size of the STOP ZONE
c. The reaction time is how long it will take the person to react to the light change. The negative acceleration is the chance of the car making it through the light. The velocity is the speed the car is going as it is approaching the light

Part B

1. stop

2. Automobile E: stop
Automobile F: stop
Automobile G: go
Automobile H: the driver would have to choose but i would try to stop if not possible I would have to go

3. Automobile J: stop
Automobile K: go
Automobile L: stop
Automobile M: the driver would have to choose but i would try to stop if not possible I would have to go

4.
a. In Intersection 1 there is no uncertainty. There is only a stop and a go zone. Intersection II has an overlap zone. Intersection III has an uncertainty area.
b. For Intersection I the choices are to either stop or go. The safe option would be to try and stop, however that may be hard to do depending on your speed.
c. For Intersection II the choices are to either stop or go. For this situation there really is no safe choice. You can take the chance of stopping short and trying to stay in the intersection or go through a red light.
d. Intersection II has an overlap zone. Intersection III has a dilemma zone.
5.

a. There is an area of uncertainty in between the STOP ZONE and the GO ZONE. This areas is 25 meters.
b. yes
c. It is the Dilemma Zone
d. It might be safer because the dilemma zone could become smaller.
6a.
At 3.7 there is 0 overlap
1.5 there is 44m overlap
6.8 there is 62m overlap
7.
a.
8.
a. For the yellow light time the increase in light time increases the size of the overlap zone. For the speed of the vehicle if the speed is decreased it becomes safer for the car to stop. For the negative acceleration rate decreasing the negative acceleration rate lessens the size of the unsafe zone. For width of the intersection making it smaller makes the intersection safer.
9a. The size of the car affects the model. The longer the car the more room it takes up and the longer it takes it to make it through the intersection.

Physics Talk

• mathematical model- formulas or equations that are used to help us understand something in the real world BUT they don't need to relate to real objects
• Yellow light model- different variable to determine whether to stop or go through a yellow light
  • determine the STOP ZONE and the GO ZONE
  • determine safety- Dilemma Zone or Overlap Zone
• GO ZONE
  • includes all positions where you can safely go through a yellow light at an intersection
  • 3 variables impact this
    • velocity of the car (v)------if velocity increases, the GO ZONE increases
    • yellow light time (ty)------if ty increases, the GO ZONE increases
    • width of the intersection (w)
  • Equation to find the GO ZONE
    • GZ= (v)(ty)-w
• STOP ZONE
  • All the positions where you can safely stop at a yellow light
  • 3 variables that impact the STOP ZONE
    • velocity- if velocity increases, then STOP ZONE increases
    • reaction time- if tr decreases, then the STOP ZONE decreases
    • negative acceleration- if a increases, then the STOP ZONE decreases
  • Equation to find the STOP ZONE
    • SZ= (v)(t)+v^2/2a-----same equation as total stopping distance
• Dilemma vs. Overlap Zone
  • Zones help determine the safety of the intersection
  • Dilemma Zone- the intersection is not safe
    • creates an area where stopping and driving is not safe
  • Overlap Zone- the intersection IS safe
    • creates an area where stopping and driving are both safe
• Limitations of the yellow light model
  • All models have limitations
  • The STOP ZONE and GO ZONE don't take car length into account

Checking Up

1. A model uses formulas or equations that are used to help us understand something in the real world.
2. The GO ZONE is an area where it is safe to proceed through the intersection at a yellow light
3. The STOP ZONE is an area where it is unsafe for you to proceed through the intersection at a yellow light
4. The Overlap Zone is an area where stopping and driving are both safe at an intersection with a yellow light
5. The Dilemma Zone is an area where both stopping and driving are not safe

Physics Plus

1. If the speed of your car increases then the size of the GO ZONE increases. If the speed of the car decreases then the size of the STOP ZONE decreases as well.
2.

3.

4.

5. Where the two lines overlap each other (up until around 20 or 25) is the Overlap Zone. The Dilemma Zone is where the the two lines separate.
6. This is possible because you could be driving slow before the yellow light and if you go to slow you may try to speed up for the yellow light, but because you are already going slow it may be difficult to reach the faster speed in time. Both of the options of stopping and going through the intersection are unsafe.
7. "Stepping on it" may help you get through the light, however that is very unsafe and because if you are going fast and don't make it in time you could run a red light and harm yourself or others around you.
8.

What do you think now

• If all yellow lights were the same amount of time then drivers would always know where the GO ZONE and the STOP ZONE were making intersections safer.
• You may not know how long the light is yellow for and drivers may not know where the STOP ZONE and GO ZONE are and the difference between the two

Essential Questions

• speed, condition of brakes, yellow light time, response time, width of intersection, negative acceleration
• You could use the GO ZONE and STOP ZONE equations: GO ZONE= (v)(ty)-w, STOP ZONE= (v)(t)+v^2/2a
• They can help you understand a yellow light intersection at different situations such as speed and distance from the light.
• This can help me in real life to make better decisions at yellow lights. It will helps me make a safer decision as to going or waiting for the next light.

Physics to Go

1.
a. GZ= (v)(ty)-w
GZ= (15)(4)-15
GZ= 45
b. SZ= (v)(t)+v^2/2a
SZ= (15)(1)+(15^2)/(2*5)
SZ= 37.5
c.
2.
a. GZ= (v)(ty)-w
GZ=(30)(4)-15
GZ= 105
SZ= (v)(t)+v^2/2a
SZ= (30)(1)+(30^2)/(2*5)
SZ= 120
Dilemma Zone
b. GZ= (20)(4)-15
GZ= 65
SZ= (20)(1)+(30^2)/(2*5)
SZ= 60
3. Reaction time does not affect the GO ZONE equation but it does affect the STOP ZONE equation
4. They will need a longer time to brake because of the condition of the car, you won't be able to slow down fast
5. In case someone tries to make it through a yellow light and ends up running a red, there is no accident because the other side waits
6. People would try and beat the clock and make an unsafe decision
7.

A. GZ= (v)(ty)-w
GZ= (20)(3)-12
GZ=48
SZ= (v)(t)+v^2/2a
SZ= (20)(1.2)+(20^2)/2(7)
SZ= 52.6
Unsafe- Dilemma
B. GZ= (v)(ty)-w
GZ= (20)(4)-8
GZ= 72
SZ= (v)(t)+v^2/2a
SZ= (20)(1.2)+(400)/2(7)
SZ= 52.6
Safe- Overlap
C. GZ= (v)(ty)-w
GZ= (20)(3)-12
GZ=48
SZ= (v)(t)+v^2/2a
SZ= (20)(1)+(400)/2(7)
SZ= 48.6
Unsafe- Dilemma Zone
D. GZ= (v)(ty)-w
GZ= (20)(3)-12
GZ=48
SZ= (v)(t)+v^2/2a
SZ= (20)(1.8)+(400)/2(7)
SZ= 64.6
Unsafe- Dilemma Zone
E. GZ= (v)(ty)-w
GZ= (20)(3.5)-12
GZ= 40.5
SZ= (v)(t)+v^2/2a
SZ= (15)(1.2)+(225)/2(7)
SZ= 34.1
Unsafe-Dilemma Zone
8. no, there are too many different variables-- different vehicle, different reaction time, different speeds

Section 7

Learning Objectives

• Recognize the need for a centripetal force when rounding a curve
• Predict the effect of an inadequate centripetal force
• Relate speed to centripetal force

What do you see

• The car is speeding around the turn
• The car is out of control
• If he continues he will get in an accident with the cars stopped ahead
• The car is on 2 wheels
• The car has the possibility of falling off of the cliff

What do you think?

• Because a curve is coming up and it is dangerous to go around it to fast because you could go into the other lane and get into an accident
• By the size of the turn. If you have a gradual turn you can go faster than one that is a sharp curve

Investigate

1. The car will continue in the same direction as where the string was let go of
2.
a. In a circle
b. We stopped it in front of us(forward), so it continued forward.
3.
a.

4.
a. 7.5 inches
6.
a. 22.55s
b. 10/22.55= x/60
26.6
c. 26.6*10= 2.66s
d. Ten revolutions is a better idea because taking it ten times would be an average of all of the turns.
e. 26.6/60= .44
7.
a. 2*pi*20= 125.66m/s
b. 125.66/2.66= 47.24
8.
a.The sandpaper will help keep the washer on the turntable for a longer period of time because it is not as slippery as the wood surface
b. 600/12.95= 46.3
46.3/10= 4.63
46.3/60= .77
c. 2*pi*20= 125.66
125.66/4.63= 27.14
9.
a. A bigger radius means a gradual turn and you don't have to slow down as much for the turn
b.

Radius(cm)	Time of 1 Rev(s)	Time of 1 Rev(s)	Time of 1 Rev(s)	Average time of 1 Rev	Circumference	Maximum Safe Speed
20	3. 55	3.52	3.16	3.41	125.66	3.55
10	3.05	1.71	1.69	2.15	125.66	3.05
3	1.85	1.19	1.05	1.36	125.66	1.85

Radius(cm)	Time of 1 Rev(s)	Time of 1 Rev(s)	Time of 1 Rev(s)	Average time of 1 Rev	Circumference	Maximum Safe Speed
20	1.27	1.98	2.03	1.76	125.66	2.03
10	2.13	1.59	1.72	1.81	125.66	2.13
3	1.81	1.38	1.10	1.22	125.66	1.81

10.
a. The truck with the bricks is heavier than the other truck and will have to slow down before the other truck has to.

Physics Talk

• Force- a push or a pull that changes the state of motion of an object
• Newton's first law (Law of Inertia)states that an object in motion will stay in motion at a constant speed and travel in a straight line unless a force acts on it
  • An object in motion or rest will stay in motion or rest unless acted on by an outside force
• Inertia- the ability of an object to resist a change in its state of motion
• The force of friction between the block and the turntable kept the block moving in a circle
• There is a force between the tires and the road that keeps an automobile moving in a circle
• Centripetal force- a force directed toward the center to keep an object in a circular path
• For the earth moving in a circle around the sun, the centripetal force is gravity
• The velocity does not change because the direction is changing
• Accelerations- changes in velocity with respect to time
• Centripetal acceleration- a change in the direction of the velocity with respect to time-- has to be in a circular path

Checking Up

1. The center of the circle
2. Centripetal Force
3. Centripetal Force
4. The velocity of the object can change even if the speed isn't changing because direction could be changing
5. Acceleration is the change in velocity with respect to time. Velocity can change when an object speeds up, slows down, or changes direction
6. Gravity

Physics Plus

Use to calculate Centripetal Force and Centripetal Acceleration

a.

b.

c.

Physics to Go

(#1-5, 7-9, 11, 12)

1. 465m/s
2. 29,900m/s
3. 5654.9m/s
4.
a. If it is going around a tight curve then the car must travel at a slower speed to make sure it does not tip
b. When the road becomes slippery, the car must be even more careful because there is less friction between the tires and the road
c. When there is a tight curve and the road is slippery it is very dangerous. You can lose control of your car because there is very little friction between the car and the road.
5. There is a centripetal force that is keeping these things going in a circle. For the moon and the earth, gravity keeps them going in a circle. For the clothes spinning in a drier, the walls of the drier keeps it spinning. One example of this is NASCAR.
7. "The driver may turn the wheels but it is the road that turns the automobile"
This means that the driver turns the steering wheel but the traction keeps the car on the road.
8. 72.9

9. Yes because they were both describing the same event. One used words from physics
11. The car is traveling at a certain speed and a certain way. If the curve becomes tighter, the car has to be able to adjust to a new speed and change their direction. Most cars cannot do this at a moments notice.
12. If the car traveling on the right side of the road lost control it would end up in the ditch to the right. It the curve was bending to the left and lost control, then it would end up going into oncoming traffic.