CbrownSafetyChapter3

=toc Chapter 3 =

Section 1
http://www.nydailynews.com/ny_local/2011/01/19/2011-01-19_driver_passenger_killed_when_car_crashes_into_median_in_the_bronx_police_say.html

A wife and husband were traveling through Brooklyn and hit a concrete block. They were both killed and the accident happened because of wet roads. The slid off the road. The concrete block has been hit before. It holds plants, but is hard to see.

What do you see? I see a car wreck that smashed the car completely. It seems to be a testing crash facility. The people in the car look fake. The accident looks very hazardous and the whole front of the car is crunched. The teddy bear is flying in the car because the child seem to have let go of it. It moved in a parabolic shape (projectile). The air bags went off because the accident was so bad. everything in the car seemed to have gone upwards or away from the car.

What do you think? There are a few things that a driver can do in order to protect themselves from an accident. Ensuring that the air bags work and that everyone's seat belt is securely buckled can help save lives. Make sure children that are younger are in car seats and that the driver has no distractions that could cause him/her to get into an accident.

Investigate (yes/no) || New Cars (1,2,3) ||
 * Safety features || Means of protection || Pre-1960 cars
 * seat belt || Keep the body from being projected out of the car || no || 1 ||
 * head restraints || Keep head stable, prevents whiplash || no || 1 ||
 * front airbags || To stop the people from moving and hitting the steering wheel || no || 1 ||
 * back up sensing system || To be able to see blind spots behind you || no || 3 ||
 * front crumple zones || To redirect shock and absorb shock || no || 2 ||
 * rear crumple zones || To redirect and absorb shock || no || 2 ||
 * side-impact beams in doors || resists side penetration || no || 2 ||
 * shoulder belts for all seats || Secure the person in the chair and keeps them from being projected out of the car. || no || 1 ||
 * anti-lock braking systems (ABS) || helps maintain control/prevents skids || no || 2 ||
 * tempered shatterproof glass || helps prevent cuts || yes || 1 ||
 * side airbags || Lessens the impact on the side of your body. Absorb short || no || 2 ||
 * turn signals || Allow other drivers to be aware of the way you are turning. || no || 3 ||
 * electronic stability control || helps resist rollovers || no || 3 ||
 * energy-absorbing collapsible steering column || prevents chest trauma || no || 1 ||

2. Assistant Analyst a) No, I wasn't surprised that I knew as much as I did. A lot of the information was common sense.

Physics Talk
 * 4WD
 * When created, more people were getting into accidents. (at first) This was because the cars could travel fast while in 4WD. Drivers felt as if they were safer with the 4WD, therefore they could travel fast without getting injured.
 * Anti-lock breaks
 * Drivers took advantage of anti-lock breaks and 4WD in the same sense. They felt safer so they drove faster. Many accidents that occurred could have been prevented if the driver had just slowed down.
 * People driving/in vehicle and pedestrians are in the same danger.
 * Automobiles started off not considering safety as much as they do now.
 * Cars didn't have seat belts, they had chrome dashboards, and solid steering columns which are all dangerous to have in a vehicle.

Checking Up 1. They put seat belts in cars, added 4WD, and anti-lock breaks. Regardless of the confidence it gives drivers to drive faster, it still helps if the driver dries slow. 2. The driver is too confident and feels safe so they drive fast regardless of the weather conditions. If they had driven slower they could have avoided being in the accident. The cars also were able to move faster when 4WD and anti-lock breaks were created.

Physics To Go 1. Seat belts F, eliminating chrome dashboards F, eliminating solid steering columns F, 4WD FRST, anti-lock breaks FR, air bags FS, turn signals R, head restraints FRST, shoulder belts F.  2. Helmets, knee/elbow pads, gloves for grip of the handle bars, turning signals, bright colors and gripped shoes. 3. Helmets, knee/elbow pads 4. Helmets, knee/elbow pads, shoes that will grip onto the grip tape

What do you think now? To protect yourself from a car accident there are multiple things a person can do. By using a signal, there will be no confusion on which way the person is turning therefore they will no have a rear end accident. By wearing a seatbelt, a person can keep their body stable in the car when it is hit. The airbags must be turned on so that shock can be prevented. Young children should all be in car seats because they are too small to be in regular seats. They can get ejected from the car if they are not securely in their seat. Putting your hands out to try to brace yourself during an accident will not help you. It may cause you to break your arms. Also, putting your legs up on the dashboard (passenger) will not help you either. It could cause back injuries and the airbags could open up on you when getting into a car accident.

Section 2
Investigate Hypothesis: A passenger involved in a car accident that is not wearing a seatbelt will be forced from the car. They will fly forward because force that happens from the car crash. The inertia of the person will be large because of the weight of the person itself and because of the collision.

Materials: Cart Play-doh person Incline String Tape

Data and observations: 2 textbooks: fell off side of cart 3 textbooks: fell forward off of cart 4 textbooks: roll forward off of car and incline

is so small so it puts too much pressure in small area which digs into his body ||  || as a result of the narrow wire. When the cart plunged forward, he moved forward as well, pushing against his wire restraint. We observed lacerations to his shoulder and legs. || the slant, he was in good condition and the ribbon was a decently sturdy seatbelt. After released down the slant the seatbelt restricted the person from falling out of the car. The damage wasn't very severe, he might have went through the windshield. Only a broken arm and maybe some injuries on the back/neck. Overall the seatbelt protected the clay person from death but no serious injuries. ||
 * Type of Seatbelt || Before Picture || After Picture || Description and Observations ||
 * Thread || [[image:threadddd_beforeee.jpg]] || [[image:thrhththththread_after.jpg]] ||  || The seatbelt holds him but the thread
 * Wire || [[image:WIRE_BEFOREOROEROEREOR.jpg]] || [[image:WIRE_AFTERRRRRR.jpg]] || The clay passenger suffered cuts
 * String || [[image:beforeclayman!.jpg]] || [[image:afterclaymannn.jpg]] || The clay man was forced forward and caused indentations on the legs. He could have been forced forward because the string was not secure enough on the clay man. ||
 * Yarn || [[image:YARN_BEFOREAAA.jpg]] || [[image:YARN_AFTEREREERER.jpg]] || The little clay man was sent flying down the incline with a two-point seatbelt made of yarn around his waist and across his body and shoulder, and crashed into the end, without significant injury. No cuts could be seen from the force of the yarn on the man and no body parts were missing or out of place. The cart hit the end of the track and the little clay man did not move sitting in place where I had placed him on the cart. ||
 * Ribbon || [[image:RIBIBIBIBIBBIN_BEFOER.png]] || [[image:RIBIBIBIBIBIBN_AFTER.png]] || Before we let our clay person go down
 * 1-in masking || [[image:mashksadgklajsdglkajdsglkdajsgbefore.jpg]] || [[image:asdjglkasdjg_masking_after.jpg]] || The clay model was sent down the incline/ramp with a seat-belt made out of tape. The tape was wrapped around his waist and than pulled over his shoulder. The seat-belt allowed the clay model to go down the incline without ending up out of the cart and with significant injuries. The clay model was still held in by the seat-belt by the end of the trial, so in all the tape seat belt worked. ||

Questions:


 * 1) Define the terms: inertia, force and pressure.
 * 2) Inertia is the tendency of a object at rest to stay at rest of a moving object to remain moving at constant speed in a straight line. Force is a interaction between two objects that results in acceleration for both or one of the objects. Pressure is the force of a certain area that is perpendicular to a surface.
 * 3) In the collision, the car stops abruptly. What happens to the “passenger”?
 * 4) The passenger's body goes forward off of the car.
 * 5) What parts of your passenger were in greatest danger (most damaged)?
 * 6) The "seat belt" caused lacerations in the legs and made the area between the legs and body thinner.
 * 7) What does Newton’s first law have to do with this?
 * 8) The body stayed at rest until the force from the cart hitting the end of the incline caused the body to jerk forward.
 * 9) What materials were most effective as seatbelts? Why?
 * 10) Softer materials that won't cause the indentations on the body. Ribbon or yarn and even string were good choices.
 * 11) Use Newton's first law of motion to describe the three collisions.
 * 12) The car crashing into another object. The body crashes into the steering wheel, dash board, or wind shield. And the organs crashing inside of you.
 * 13) Why does a broad band of material work better as a seatbelt than a narrow wire?
 * 14) The wire is very thin and strong and can cut the person if the car is going fast enough

Conclusion: · Using Newton's First law of Motion, explain why a seat belt is an important safety feature in a vehicle. What factors affect the effectiveness of a seatbelt? What would you need to consider when designing a seatbelt for a race car? Use specific observations from this investigation to support your answers to these questions. Seat belts help the body after a collision takes place. It keeps the body from jerking forward. This relates to Newton's first law because an external force is acting on the car which is acting on the body, seat belts help lessen the force that is put on the driver/passengers.

· Explain at least 1 cause of experimental error. Be sure you describe a specific reason. The clay man could have been put in a different spot during trials. This could be the reason why the body didn't fall off of the cart on certain trials and did on others.

· How would you improve the results of this lab? (In other words, what would you change about the materials or procedure to eliminate or reduce the experimental error you describe above?) There would be an actual seat in the car that a seatbelt can be put on easily. It was difficult putting the seatbelt on and I felt as if it may have not been as secure. A better adhesive would have also greatly helped. The incline was a perfect thing to use a more reliable object to use for height would have made the experiment more accurate. The incline fell off the book stack at certain points which may have affected our seatbelt adhesive.

Section 3
Objective:


 * How does an air bag protect you during an accident?

Hypothesis: Air bags keep the skull from breaking. It allows the body to stay in place and not hit the dashboard when an accident occurs. It keeps bones from breaking and helps the body stay intact.

Materials: -Egg -Plastic Bag -Ruler -Baking powder

Data and observations: Add more columns/rows as needed. Calculations: Show equation(s), numbers plugged in, and answer with correct units. Add columns in your data table to include these results.
 * What is the gravitational potential energy in each trial?
 * [[image:Picture_1.png]]
 * Egg # || Dropped Height || Cracked or Smashed? || Description & Observations ||
 * 1 || 2 cm || crack || there was a very tiny hairline crack on the bottom of the egg. no yolk came out ||
 * 1 || 4 cm || crack || crack got bigger, there is still no yolk ||
 * 1 || 6 cm || crack || egg is starting to break more. there are multiple cracks ||
 * 1 || 8 cm || crack || there are more indents and more noticeable cracks ||
 * 1 || 10 cm || crack || the bottom is becoming flattened and the cracks are moving towards the center of the egg ||
 * 1 || 12 cm || crack || yolk is starting to show and there are a lot of cracks ||
 * 1 || 14 cm || crack || there is some yolk coming out ||
 * 1 || 16 cm || smashed || the bottom of the egg is smashed and there is a lot of yolk coming out ||
 * 1 || 18 cm || smashed || the yolk continues to pour out at the height is now 5 cm ||
 * 1 || 20 cm || smashed || the yolk is still coming out and the height is now 4.8 ||
 * 1 || 22 cm || smashed || the yolk is almost out but not quite ||
 * 1 || 24 cm || smashed || part of the shell is almost off, the yolk is coming out and the height is now 4.4 cm ||
 * 1 || 26 cm || smashed || the yolk has not come out yet, but the egg is smashed. it is now 3.9 cm ||
 * 1 || 28 cm || smashed || parts of the shell fell off and the egg is now 3.7 cm ||
 * 1 || 30 cm || smashed || 3 cm, yolk is almost out ||
 * 1 || 32 cm || smashed || the egg is completely smashed and the yolk is out. the height is 2.6 cm ||
 * 2 || 32 cm ||  || Buried: 1.5 cm Above: 3.5 cm ||
 * 2 || 34 cm ||  || Buried: 1 cm Above: 4 cm ||
 * 2 || 36 cm ||  || Buried: 1.7 cm Above: 3.2 cm ||
 * 2 || 38 cm ||  || Buried: 2 cm Above: 3 cm ||
 * 2 || 40 cm ||  || Buried: 2. 3 cm Above: 2.7 cm ||
 * 2 || 42 cm ||  || Buried: 2.8 cm Above: 2.4 cm ||
 * 2 || 44 cm ||  || Buried: 1.6 cm Above: 3.4 cm ||
 * 2 || 46 cm ||  || Buried: 2.4 cm Above: 2.6 cm ||
 * 2 || 50 cm ||  || Buried: 1.7 cm Above: 3.2 cm ||
 * 2 || 60 cm ||  || Buried: 3 cm Above: 2 cm ||
 * 2 || 70 cm ||  || Below: 3.5 cm Above: 1.7 cm ||
 * 2 || 80 cm || cracked || Below: 3.4 Above: 1.8 cm ||
 * 2 || 85 cm || cracked || Below: 3.8 Above: 1.4 cm ||
 * 2 || 90 cm || cracked || Below: 2.5 cm Above: 2.5 cm- yolk is visible ||
 * 2 || 95 cm || cracked || Below: 2.5 cm Above: 2.5 cm- yolk is out ||

*Read the Physics Talk p279 - 287 before answering the following questions. * Questions: 1.This investigate is an analogy for a person in an automobile collision. What does the egg represent? What does the table represent? What does the flour represent? The egg represents the person in the car. The table represents the collision. The flour represents the air bag 2. Define Kinetic energy and work KE=1/2mv^2. Kinetic energy is the energy obtained by a moving object. Work=FD. Work is the force applied over a certain distance. 3. What factors determine an object's kinetic energy? The factors that determine an objects kinetic energy are the mass and the velocity of the object because those are the components of the equation KE=1/2mv^2. 4. When work is done on an object, what is the effect on the object's kinetic energy? Work can either increase or decrease the kinetic energy. This depends upon the direction the object is moving in. If the work is moving in the same direction as the object, it can increase. If the work is acting in the opposite direction stopping the object, it decreases kinetic energy. 5. How does the force needed to stop a moving object depend on the distance the force acts? The object stopping the moving object is work. The less the distance, the greater the force. 6. What difference does a soft landing area make on a passenger during a collision? The work done on a soft landing area decreases the kinetic energy of the object. The area of the soft landing lowers the damage of the impact, because with a hard landing the object with just crash, with a soft impact it allows the object to have some cushion. 7. How does a cushion reduce the force needed to stop a passenger? The cushions apply padding and more room for the person to move with. It also increases the distance for the person to stop, because the cushion moves back and forth. The stopping distance is greater. And the force required decreases 8. What does the law of conservation of energy have to do with this? Newton's first law states that an object in motion or rest stays in motion or rest until an unbalanced force acts upon it. The person is the object in motion and the airbag is the unbalanced force stopping the person from hitting the dashboard or even falling out of the car. · Explain at least 1 cause of experimental error. Be sure you describe a specific reason. The egg could have been dropped on different sides, therefore there wouldn't be an accurate measure of the egg falling. Also, the bag may have gotten in the way of the drop and have messed up the measurements. · How would you improve the results of this lab? (In other words, what would you change about the materials or procedure to eliminate or reduce the experimental error you describe above?) I would have used a different kind of bag or piece of plastic that the crease wouldn't affect the way the egg fell. Also I would have used a measure that was constant and not constantly moving. (A stand that held the ruler rather than a student hand)

Section 5
Physics To Go 1. The vehicles will exert forces on each other. The vehicle moving has a larger momentum, therefore there vehicle that is stopped will receive the moving vehicle's momentum. This will cause the vehicle at rest to move. The car that is being hit will take the momentum of the bullet car and continue to move. 4. They prefer players that weigh 140 kg because they have a higher momentum. Having a heavier weight and running at the same speed as a player with a lower weight will give the heavier player an advantage. If a smaller player, say 90 lbs was running towards the quarterback, the linemen can easily stop the lower weight player because their momentum is larger. The 90 lb player will not be able to knock down the 300 lb linemen. 5. The vehicles speed and mass (momentum) determines who will get knocked down in a head on collision. If a truck is going 5 mph and a smaller car is driving 75 mph, the truck would be more affected. If a truck was driving faster than a smaller car, the smaller car would get affected because of the trucks momentum. 6. p=mv p=(1000kg)(10m/s) p=10,000 kgm/s

10,000kgm/s=(10,000m/s)(v) (10,000kgm/s) / (10,000m/s)=v 1 m/s = v The truck would need to travel at 1 m/s in order to have the same momentum.

Section 6 Objective: What physics principles do the traffic-accident investigators use to "reconstruct" the accident?

Materials: List any materials used and draw a labeled diagram of your set-up (alternatively, include a snapshot or video).

Procedure:
 * 1) Place a motion detector at the right end of a track. Open up data studio. Dump "Velocity" into "Graph" display, and enlarge this.
 * 2) Place a cart on the middle of the track with the velcro to the right. Call this the "target cart." Place a second identical cart on the right end of the track. Call this the "Bullet cart".
 * 3) Click "Start" on Data Studio, and then push the bullet cart very gently towards the target cart so that they collide and stick together. You may need to practice this a few times. Be sure to get your body out of the way of the motion detector!
 * 4) Examine the graph produced by the motion detector. Using the Smart Tool, find the velocity right before and right after the collision. Record this in your data table.
 * 5) Vary the masses of the carts and repeat the process 5 times.

Data and observations: Add more columns/row as needed.
 * Mass of Bullet Cart (kg) || Mass of Target Cart (kg) || Speed of Bullet Cart(m/s) || Speed of Target cart (m/s) || Combined masses (kg) || Final Velocity of both carts (m/s) || Initial Momentum (of bullet cart) || Initial Velocity (of target cart) || Total Initial Velocity (of both carts) || Final Momentum (of both carts) ||
 * 0.4977 || 0.494 || .58 || .70 || .9917 || .39 || .29 kg m/s || .35 kg m/s || 1.26 kg m/s || .39 kg m/s ||
 * .9977 || .494 || .52 || .37 || 1.4917 || .37 || .52 kg m/s || .18 kg m/s || 1.36 kg m/s || .55 kg m/s ||
 * .4977 || .994 || 1.02 || .26 || 1.4917 || .26 || .51 kg m/s || .26 kg m/s || 1.91 kg m/s || .39 kg m/s ||
 * .9977 || .994 || 1.68 || .35 || 1.9917 || .35 || 1.68 kg m/s || .35 kg m/s || 4.04 kg m/s || .70 kg m/s ||
 * 1.4977 || .494 || .69 || .72 || 1.9917 || .44 || 1.03 kg m/s || .36 kg m/s || 2.81 kg m/s || .88 kg m/s ||
 * .4977 || 1.494 || .83 || .21 || 1.9917 || .21 || .41 kg m/s || .31 kg m/s || 2.07 kg m/s || .42 kg m/s ||

Calculations: Show equation(s), numbers plugged in, and answer with correct units. Add columns in your data table to include these results. Trial 1 p=mv p=(.4977 kg)(.58 m/s) p= .29 kg m/s For trials 1 and 5, the initial velocities for the target cart were different. In all the other trials, they were the same. Trial 1, example Target(initial)=.70 m/s p=mv p=(.494 kg) (.70 m/s) p=.35 kg m/s Trial 1 p=mv p=(.4877+.494 kg) (.58+.7 m/s) p= (.9817 kg)(1.28 kg) p=1.26 kg m/s Trial 1 p=mv p=(.9917 kg) (.39 m/s) p=.39 kg m/s
 * 1) Find the initial momentum of the bullet cart for each trial
 * 1) Find the initial momentum of the target cart for each trial.
 * 1) Find the sum of the initial momenta of the two carts for each trial.
 * 1) Find the final momentum of the combined carts for each trial.

*Read the Physics Talk p312 - 315 before answering the following questions. * Questions:
 * 1) Compare the initial momenta (calc 3) to the final momentum (calc 4). (Allow for minor variations due to uncertainties of measurement.)
 * 2) The initial seems to be always larger than the final momentum.
 * 3) List the 6 types of collisions (top of page 312) and a brief description.
 * 4) a) An object in motions hits an object that is at rest and they move off together at the same speed; b) Two objects at rest explode by the release of a spring between them and move off in different directions; c) An object in motion hits an object at rest, the object that hit the stationary object stops and the stationary object moves off; d) An object in motion hits an object at rest and they both move off with different speeds; e) Two objects in motion hit each other and continue to move off in different speeds; f) Two objects in motion hit each other and move off together with the same speed
 * 5) Which types of collisions are definitely inelastic? How do you know?
 * 6) If an object hits an at rest or a moving object and they continue off together at the same speed almost "stuck" to each other. This is inelastic because the objects do not bounce off of each other and stay together after the collision.
 * 7) Which types of collisions are definitely elastic? How do you know?
 * 8) If an object hits another object at rest or an object that is moving and they move apart from each other after the collision. They could either go in different directions or continue moving at different speeds but are not together. I know this because an elastic collision is one that takes place and after the cars are not together. They are separate and "bounce" away from each other after the collision.
 * 9) Define the law of conservation of momentum.
 * 10) The total momentum before a collision is equal to the total momentum after a collision unless an external force acts on the system.
 * 11) Use the law of conservation of momentum to describe what happens when a cue ball hits the 15 balls in the middle of the pool table.
 * 12) The momentum that the cue ball has before it hits the other balls is transferred to the other balls which causes them to move with the same momentum that the cue ball had before the collision.

Conclusion: · Based on the law of conservation of momentum, how can the traffic-accident investigators use to "reconstruct" the accident? What does it mean to "conserve" momentum? If they know the mass and velocity that the car was traveling, they could reenact the situation and see what the momentum of the car went into/ where it was transferred to. They could crash the car into another car of the same mass as the original accident and see whose fault the accident really was and who transferred their momentum into who. · Explain at least 1 cause of experimental error. Be sure you describe a specific reason. The cart could have been pushed at different speeds which would affect the momentum and how it hit the bullet cart. Also, the graph could have been misread. · How would you improve the results of this lab? (In other words, what would you change about the materials or procedure to eliminate or reduce the experimental error you describe above?) I would have had the bullet car move at a constant rate rather than an uneven push given by a student. Also, there would have been a more varied mass to see how the bullet cart would affect the target cart at higher masses. I also would have liked to test out more masses on the target cart to see if it would affect the bullet cart.