8. Safety Concerns-restraints

In this activity, you will learn about bike, bus and auto restraints safety.  You also will perform experiments illustrating safety features using eggs.

Safety

 

Transportation safety includes bike safety, pedestrian safety, car safety and passenger (auto, air, and train) safety and other related areas.  Airline safety can also be included in this topic.  Although airlines have a better safety record than automobiles, airports are becoming more congested each year. 

Moving objects have momentum.  Newton's First Law sates that unless an outside force acts on an object, the object will continue to move at its present speed. 

The sad fact is that yearly thousands of people still die in traffic crashes. When a vehicle is involved in a crash, passengers are still traveling at the vehicles original speed at the moment of impact. When the vehicle finally comes to a complete stop, unbelted passengers slam into the steering wheel, windshield or other part of the vehicle's interior.

Seat belts are your best protection in a crash. They are designed so that the forces in a crash are absorbed by the strongest area of your body -- the bones of your hips, shoulders and chest. They keep you in place so that your head, face and chest are less likely to strike the windshield, dashboard, other vehicle interiors or other passengers. They also keep you from being thrown out of a vehicle.

Did you know that airbags save over 1,500 lives per year? Amazing isn't it. For adults, airbags can seriously reduce the chance of injury in a crash that's a good thing. What's not so good is that the force of an airbag when it's deployed can severely injure small children.

An air bag is made of coated fabric and is stored in a module mounted on the steering wheel. Crash sensors, which activate upon impact at speeds of 10-15 miles per hour, are mounted in several locations on the car chassis.  In a crash, the sensors ignite a chemical, sodium azide, which releases harmless nitrogen gas to instantly inflate the bag. As the driver or passenger is thrown into the bag, it applies a restraining force. Even though this entire process happens in only 1/25th of a second, the added time is enough to slow momentum to prevent serious injury.

 

 

 

 

 

 

 

 

 

 

 

 

 

8a. Safety Challenge

1.      Answer questions on worksheet about bicycle, bus and automobile safety.

2.    Tally up your scores and give to instructor

 

8b. Automobile Safety

Purpose: Design ways to cushion an egg that is dropped through the air. Using the theories behind air bags in automobiles, find the best way to protect it from impact so you can drop it further.

 

1.      Taking the box of materials you have 30 minutes to design and construct a safety compartment for your egg.

 

2.     Insert a raw egg into the compartment.

 

3.    Find the mass of each compartment and record on data sheet (note: lighter weights give higher final point values).

 

4.    Drop each compartment one at a time and record if it survives a 3-foot fall.

 

5.    For those eggs that survive, the egg compartment will be dropped 6 feet.

 

6.    The surviving egg compartments will be dropped 9 feet.

 

7. Record your data on worksheet and compute your final score

 

 

 

 

 

 

 

 

 

 

Engineering Scoop

 

When you dorp the egg, the packaging material either slows down the fall or cushions the egg until it stops falling. The material can change the coefficient of restitution or make the impact more elastic. Things that are elastic return almost to their original shape after they've been stretched or squashed by a force.

 

Discussion

 

¨     Did the packing material slow the descent or protect the egg in some other way?

¨     What could you change so that it does?

¨     What happens if you change the height of the drop?

¨     What happens if you change how you arrange the materials?

 

Choose one thing to change (that's the variable) and make a prediction.

 

¨     What happens to the egg's momentum?

¨     What would happen if you were dropping the egg directly on a concrete floor?

¨     What are some of the theories that can be used to transfer the momentum of the egg?

¨     Would a parachute attached to the egg provide enough cushion to keep it from breaking? How high could you drop an egg attached to a parachute?

¨     Is it possible to design a springing car to absorb the impact of accidents by itself.

¨     Does the height of the drop make a big difference? Remember: Force = Mass times acceleration