Section 2: Life and Death: Before and After Seat Belts Unit 2: Safety Section 2: Life and Death: Before and After Seat Belts

Investigation What part of the body hit first on your clay model during a low speed? What happened when you increased the speed? Is there a greater damage to the clay figure?

Investigate When the driver continues to move in the direction of the car; what part of Newton’s Law is this? When the seat belt stops the figure; what part of Newton’s Law is this? Where is the most “trauma” going to occur on the figure?

Talk How many parts are there to Newton’s Law 3 Using the experiment that you conducted above, describe the three parts of Newton's Law and how they were showing in the experiment? Clay figure in car at rest, Clay figure continues to travel once the car stops, stops due to an unbalanced force (“wall” or seat belt)

Talk What limitations does the clay figure have when demonstrating collisions? What happens to internal organs during a collision?

Talk Which is better, a thin wire or a broader strip for the seat belts? The spreading of the force over an area is called what? Pressure

Think Now Why is a seat belt an important safety feature in a vehicle? What needs to be considered when designing a seat belt?

PTG: 1, 3, 8-10 A. You step on the brakes to stop your car. You and the car are moving forward. The brakes apply a force to the tires and stop them from rotating. Newton’s law states that an object in motion will remain in motion unless a force acts upon it. In this case, the force is friction between the ground and the tires. You remain in motion since the force that stopped the car did not stop you.

PTG: 1, 3, 8-10 B. You step on the accelerator to get going. You and the care are stopped. The engine provides a force to turn the wheels, which in turn causes the car to move forward. Inertia will keep you still unless a force acts upon you. This force is provided by the seat back which pushes you forward at the same rate as the car.

PTG: 1, 3, 8-10 C. You step on the brakes, and an object in the back of the car comes flying forward. The object was moving with the same velocity as the car. The force which caused the car to stop, was not acting on the object. Inertia of the object kept the object moving in a straight path (until it hits the driver or the windshield)

PTG: 1, 3, 8-10 D. A vehicle is involved in a collision and a passenger is wearing a seat belt. You and the car are moving forward. The other vehicle causes an unbalanced force that is equal and opposite in direction to the drivers vehicle. You continue to move forward until the seat belt you are wearing acts an unbalanced force on you causing you to stop the forward motion due to inertia.

PTG: 1, 3, 8-10 3. Inertia states that a person will continue to move in the same direction as the skateboard, thus indicating the need for helmet, knee pads, and gloves

PTG: 1, 3, 8-10 8. First collision: glove hitting head; second collision: head moves backward, and he brain collides with the interior of the skull; third collision: elasticity of the brain attached to the brain stem, causes the brain to move toward the back of the brain colliding with the internal back of the skull.

PTG: 1, 3, 8-10 9. Bed of nails: We know: Area: 1.6 m x 0.5 m = 0.8 m2 Force: 500N; each nail is 0.5 N P = Force/Area Pressure= 500N/0.8m2 = 625 N/m2 If we assume that each nail is 0.5N and know the total pressure of 1000 nails, we can determine the area per nail. 0.5 N / 625 N/m2 = .0008 m2 Take the square root = √.0008 = .03 m or 3 cm

PTG: 1, 3, 8-10 10. Modifications for a seat belt on: Plane Train Bus

Unit 2: Section 2 Quiz Seat Belts

1. When an elevator going down comes to a stop, blood tends to rush from the occupants’ heads. This phenomenon is best explained by a.) conservation of energy b.) Newton’s first law of motion. c.) action – reaction. d.) the law of universal gravitation.

2. A dull knife does not cut as well as a sharp knife when pushed equally hard. A sharp knife cuts better because it a.) requires more energy b.) continues in motion with a constant speed. c.) has a longer edge. d.) exerts greater pressure.

Imagine you are riding in an automobile and the following events occur Imagine you are riding in an automobile and the following events occur. Describe which parts of Newton’s laws applies to each event? A. rest B. motion C. unbalanced force 3.) A large box in the truck slides forward each time the brakes are applied. 4.) You feel you are “pushed back” into the seat when the automobile accelerates. 5.) When you come to a quick stop, your seat belt stops you from moving forward.

6. What is the pressure when a force of 10 N is applied to an object with an area of 0.2m2? Remember: P = F/A

7. A snowboarder weighs 600N. The area of the snowboard is 0. 5m2 7. A snowboarder weighs 600N. The area of the snowboard is 0.5m2. What is the pressure on the snow? Remember: P = F/A

8.A fisherman with a mass of 75kg falls asleep on his four-legged chair of mass 5 kg. If each leg of the chair has a surface area of 0.00025 m2 in contact with the ground, what is the average pressure exerted by the fisherman and chair on the ground? Remember: P = F/A

Rank the following from highest pressure to lowest pressure upon the ground: A. The atmosphere at sea level (equal to 100,000 N/m2) B. A 7000-kg elephant with total area 0.5 m2 in contact with the ground C. A 650 N lady in high heels with total area 0.005 m2 in contacting with the ground D. A 1600-kg car with a total tire contact area of 0.2 m2 Enter the Highest Pressure Example choice. Enter the next lowest pressure compared to 9. Enter the next lowest pressure compared to 10. Enter the Lowest Pressure Example choice.

Quiz Answers

1. When an elevator going down comes to a stop, blood tends to rush from the occupants’ heads. This phenomenon is best explained by a.) conservation of energy b.) Newton’s first law of motion. c.) action – reaction. d.) the law of universal gravitation.

2. A dull knife does not cut as well as a sharp knife when pushed equally hard. A sharp knife cuts better because it a.) requires more energy b.) continues in motion with a constant speed. c.) has a longer edge. d.) exerts greater pressure.

Imagine you are riding in an automobile and the following events occur Imagine you are riding in an automobile and the following events occur. Describe which parts of Newton’s laws applies to each event? A.rest B. motion C. unbalanced force 3.) A large box in the truck slides forward each time the brakes are applied. 4.) You feel you are “pushed back” into the seat when the automobile accelerates. 5.) When you come to a quick stop, your seat belt stops you from moving forward.

6. What is the pressure when a force of 10 N is applied to an object with an area of 0.2m2? (2 points) Remember: P = F/A 50 N/m2

7. A snowboarder weighs 600N. The area of the snowboard is 0. 5m2 7. A snowboarder weighs 600N. The area of the snowboard is 0.5m2. What is the pressure on the snow?. Remember: P = F/A 600 / 0.5 = 1,200 N/m2

8.A fisherman with a mass of 75kg falls asleep on his four-legged chair of mass 5 kg. If each leg of the chair has a surface area of 0.00025 m2 in contact with the ground, what is the average pressure exerted by the fisherman and chair on the ground? Remember: P = F/A Force = 75kg + 5kg = 80kg * 10 m/s/s = 800N 800N / (.00025*4) is .001m2 = 800,000 N/m2

Rank the following from highest pressure to lowest pressure upon the ground: A. The atmosphere at sea level (equal to 100,000 N/m2) B. A 7000-kg elephant with total area 0.5 m2 in contact with the ground C. A 650 N lady in high heels with total area 0.005 m2 in contacting with the ground D. A 1600-kg car with a total tire contact area of 0.2 m2 Enter the Highest Pressure Example choice. Enter the next lowest pressure compared to A. Enter the next lowest pressure compared to B. Enter the Lowest Pressure Example choice. 9. 140,000 B 10. 130,000 C 11. 100,000 A 12. 80,000 D