Discussion and activities about car safety (Investigation)

Here are some ideas on discussions and activities related to car safety.

Exercise 1

Outline the relationship between speed, distance and time, and describe how to convert between common units of these variables. In your answer, explain how to find values for these variables using distance vs time graphs and speed vs time graphs.

 

Exercise 2

Identify and describe all the components that affect the calculation of a car’s total stopping distance.

 

Exercise 3

Research at least 2 of the following features of cars that are crucial to driver safety:

I. Car Tires.

What are the factors that affect the usable life of tires? What are the warning signs that you should check for if you believe your tires are wearing out?

II. Vehicle Braking Systems.

How many different types of braking are there available? What are they and how do they work? Which type is the most commonly used in cars?

III. Airbags.

How do airbags protect vehicle occupants? What does SRS stand for and what does it mean? How effective are side airbags compared to frontal airbags? Present your findings with appropriate statistics for evidence.

IV. Seat Belts.

What exactly do they protect against? How does a “sash” belt differ from a three-point belt? What legislation in Australia has been passed regarding seat belts?

V. Driver Fatigue.

Between what times of the day are drivers especially vulnerable to fatigue? What are some symptoms of driver fatigue? Research some recommendations by government traffic authorities on how to avoid the occurrence of driver fatigue.
 

Exercise 4

Set up an Excel spreadsheet similar to the one below, showing how BAC values change for individuals when weight, number of standard drinks consumed and hours of drinking are varied. Plot a graph that shows how BAC specifically changes for a man and woman who both weigh 65kg and have had 5 standard drinks, when the number of hours of drinking is varied.

How does the graph change if 6 standard drinks are consumed instead of 5? Do you think the current government laws sufficiently protect road users from intoxicated drivers?

Suggested Answers to Car Safety Exercises

Exercise 1:

Outline the relationship between speed, distance and time, and describe how to convert between common units of these variables. In your answer, explain how to find values for these variables using distance vs time graphs and speed vs time graphs.

Structure of Answer:

Students should at a minimum present the S=D/T relationship. Students should already be familiar with these conversions.

Encourage students to describe relationship in words as well as using practical examples.

Ask students in what order they perform unit conversion in problem solving--> before or after solving the problem?

Slope equation should indicate thorough understanding of concepts but is optional.

Finding distance is required, finding acceleration is optional.

On distance vs time graph -->car has stopped

On speed vs time graph --> car is moving at constant speed

 

Exercise 2:

Identify and describe all the components that affect the calculation of a car’s total stopping distance.

Structure of Answer:

Students should be able to state relationship v = u + a t and s = u t + \frac{1}{2} a t^{2}.

Check carefully to ensure students don't get confused between s (which represents displacement in physics) and S, the speed.

Final velocity is zero for calculations involved in this module, as car must come to a stop. Make sure students understand this concept.

In the equations v = u + a t and s = u t + \frac{1}{2} a t^{2},

a is acceleration, which must be negative when decelerating if motion is in one dimension. You might like to tell students that deceleration is not always the opposite of acceleration if motion is in 2 or more dimensions, but this may be confusing.

Students should be aware that human reaction time varies with each driver.

Reaction time x Speed of vehicle = Reaction time distance

Exercise 3:

Research at least 2 of the following features of cars that are crucial to driver safety:

Structure of Answer:

I. Car Tires.

• Tire over-inflation or under-inflation.
• Shock absorbers wearing out
• Feathering & wheel alignment

Good research will include pictures of different signs of tire tread wear. Worn-out tires are dangerous because of skidding risks (especially in rain/snow), and passengers will also encounter jolting during the drive. Blowouts and tire punctures are also common. Gas is also used inefficiently.

II. Vehicle Braking Systems.

• Frictional brakes-->drum brakes and disc brakes
• Pumping brakes
• Electromagnetic brakes
• Peak force, Power, Pedal feel, Drag etc

Encourage students to use diagrams in their explanations. Check that students have not just copied and pasted from Wikipedia. Responses should not be too long, dot points listing advantages and disadvantages of each type will be adequate.

III. Airbags.

• Airbags cushion impact and protect passengers against the car's interior.
• SRS=Supplemental Restraint System
• Side airbags protect from pelvic and lower abdomen injuries.

Helpful link. Statistics should be Australian-based. Students do not need to know the chemical formulae and reactions involved in airbags. They only need to write about the basic concepts involved.

IV. Seat Belts.

• Safety belts secure passengers against harmful movement in a collision.
• Seat belts in cars are usually 3-point belts, unlike aircraft lap belts.
• Locking retractors and pretensioners could also be explored.

See Road Rules 2008 and the Road Transport (Safety and Traffic Management) Act 1999 for more information on Australian seat belt legislation.

V. Driver Fatigue.

• 4 times more likely to have a fatal fatigue crash if you’re driving between 10pm and dawn.
• Get a good night's sleep before a long trip, share driving to avoid fatigue problems, etc
• Yawning, poor concentration, tired eyes, etc

The Transport: Roads & Maritime Services website has a large amount of information concerning driver fatigue. Student should be familiar with ads like Stop. Revive. Survive. 3 or 4 symptoms of driver fatigue and 2 or 3 prevention measures should be sufficient to demonstrate understanding.

 

Exercise 4:

For the specific problem, BAC of man is:

\frac{10 \times 5 - 7.5 H}{6.8 \times 65}

For the specific problem, BAC of woman is:

\frac{10 \times 5 - 7.5 H}{5.5 \times 65}

BAC should be higher when number of standard drinks is increased, and when hours of drinking is low. BAC is higher for women than for men, for the same values of standard drinks and hours of drinking.

 

Exercise 5:

Example-

For speed of  60 km/h, speed is equivalent to 16.667 m/s.

\text{Reaction time distance} = 16.667 \times 1.35

\text{Reaction time distance} = 22.50045 m

v = u + a t gives:

t = \frac{0 - 16.667}{- 5}

t = 3.3334 s

s = u t + \frac{1}{2} a t^{2} gives:

s = 16.667 \times 3.3334 + \frac{1}{2} \times \left( - 5 \right) \times 3.3334^{2}

s = 27.778 m

\text{Total stopping distance} = 50.27845 metres

Which is less than the 56 metres presented in the table.

The parameters provided should give theoretical stopping distances that are less than those in the table, for all speeds. Students should show working in their calculations, and know how to use the equations v = u + a tand s = u t + \frac{1}{2} a t^{2}.

Factors not considered in calculation include:

• Road conditions (wet/dry surface, gravel)
• Weather and its effect on vision (rain, hail, snow)
• Human factors (eg distractions, cellphone, awareness, alcohol influence)
• Driving experience and driver age
• Condition of tires & braking system
• Vehicle weight

Students should discuss at least 1 human factor, 1 vehicle factor and 1 environmental factor in their answer.

Answers will involve direct analysis of the statistics taken from sources like the ABS and the Road Deaths Database.

2012 statistics can be found here: ABS 

The Australian Road Deaths Database can be found here: Database 

Students should discuss different causes of car crashes like drunk driving and fatigue. Students should also discuss danger spots for car crashes such as rural roads and poorly maintained highways. The time of the crash occurrences should also be considered, as well as whether the crash involved P-platers and the ages of the drivers involved.