CH3_OringerP

**
 * Chapter 3toc

**Section 1**
Motorcyclist Dies in Queens Crash; 2nd Driver is Charged On January 10th, a man from Freeport was arrested after driving drunk and killing a motorcyclist. He fled the scene in Queens. Dwan Gonzales, 44, the victim, was riding a motorcycle on the Long Island Expressway and was hit from behind by a Mercedez Benz. The driver, Shamel Campell, was charged with driving while intoxicated and additional charges are likely. www.nytimes.com

__What do you see?__ A car crashes and the front is all smashed up and pushed in. The body is launched forward against the airbag on the wheel. the back bumper is flying offand it looks like the car was going fast

__What do you think?__ I would protect myself from a serious injury by always wearing a seatbelt and checking that my car needs no repairs.

__Investigate__ 2. I got 10 points, so I am a Novice Analyst. I am surprised with this because I thought I knew more about safety that I actually do.

(yes/no) || New Cars (1,2,3) ||
 * ** Safety features ** || Means of protection || Pre-1960 cars
 * seat belts || keeps driver and passengers inside car || n || 1, all ||
 * head restraints || prevents whiplash || n || 1, all ||
 * front airbags || cushions during a collision || n || 1, all (driver's side) ||
 * back up sensing system || allows to see in blind spots while backing up || n || 3, few ||
 * front crumple zones || increase collision distance reducing impact || n || 1,2, all, some ||
 * rear crumple zones || increase collision distance reducing impact || n || 2, some ||
 * side-impact beams in doors || resists side penetration || n || 2, some ||
 * shoulder belts for all seats || keeps passengers in seats during collision || n || 1, all ||
 * anti-lock braking systems (ABS) || helps maintain control/ prevents skids || n || 2, some ||
 * tempered shatterproof glass || helps prevent cuts || y || 1, all ||
 * side airbags || protects head/torso in side collisions || n || 2, some ||
 * turn signals || warns other drivers of actions || y || 1, all ||
 * electronic stability control || helps resist rollovers || n || 2, 3, some, few ||
 * energy-absorbing collapsible steering column || prevents chest trauma || n || 1, all ||

__Physics Talk__ Vehicle Safety people in vehicles are not the only ones in danger- pedestrians are too manufacturers have to be aware of vehicle safety not safe: no seat belts, chrome dashboards, solid steering columns four wheel drive - more accidents maybe due to tendency of drivers to increase speed under the impression that the safety features will protect them

__Checking Up__ 1. Three ways manufacturers have made vehicles safer: seat belts, turn signals, tempered shatterproof glass 2. explanation for increased crashing in 4WD: traveling greater distances, drivers get the impression that the feature will protect them so they increase speed, a lot are being used day to day

__PTG__ 1. 10 safety features: turn signals (F,R,S), side airbags (S, T), tempered shatterproof glass (F,R,S,T), shoulder belts (F,R,S,T), side-impact beams in doors (S), rear crumple zones (R), front crumple zones (F), seat belts (F,R,S,T), head restraints (F,R), front airbags (F, R, T) 2. bike safety features: helmet, wrist guards, knee pads, reflector 3. in-line skating safety features: helmet, knee pads, wrist guards, shin guards, thick wheels 4. skate boards safety features: helmet, knee pads, wrist guards, a touch surface

__What do you think now?__ You can protect yourself from serious injury by wearing your seat belt, using turn signals, checking the protective features of a car, and activating all protection features.

Section 2
Investigate  Objectives:
 * What happens to a passenger involved in a car accident without and with a seatbelt?
 * What factors affect the passenger’s safety after a collision?
 * How would a seat belt for a race car be different from one available on a regular car?


 * Hypothesis:** Respond to each of the above objectives fully.
 * Without a seatbelt: the passenger can launch through the windshield, fly through the window, or smack their body against what is in front of them.
 * With a seatbelt: the passenger is secured in their seat and will be jerked forward, but will be snapped back to the seat.
 * Factors that affect passenger's safety after a collision: interior surfaces, strength of seat belt, exterior surfaces
 * A seat belt for a race-car would be stronger and tighter because the car is moving faster, and if the driver wasn't strapped in tight enough, he/she would thrown forward with more force.

cart, clay, ramp with end stop, wire, thread, string, yarn, ribbon, rubber bands, textbooks
 * Materials:** List any materials used and draw a labeled diagram of your set-up (alternatively, include a snapshot or video).
 * Procedure:**
 * 1) Make a clay figure and then place the figure in the cart.
 * 2) Arrange a ramp so that the endstop is at the bottom of the ramp.
 * 3) Adjust the height of the ramp to make a very shallow incline.
 * 4) Send the cart down the ramp.
 * 5) Very gradually increase the height of the ramp until significant “injury” happens to your figure. Make a note of this height. (**.365 meters)**
 * 6) Fix your clay figure. Create a seatbelt for the figure and take a "Before" picture and post in your data table.
 * 7) Send your cart and passenger down the ramp at the same height as in Step 5. Be sure to record your observations specifically and carefully. Take an "After" picture and post in your data table to supplement your written observations.
 * 8) Repeat Steps 6 and 7, using different types of material for the seatbelt.

Data and observations: Injury Height with no seatbelt: _ m

through his body and sliced his neck. || 6 ||
 * **//Type of Seatbelt//** || //**Before Picture**// || //**After Picture**// || //**Description and Observations**// || //**Group**// ||
 * Thread || [[image:theadmadread.jpg width="256" height="192"]] || [[image:thread_madread_2.jpg width="256" height="192"]] || Arm chopped off. The seat belt cut
 * Wire || [[image:hershey_kissboybefore.jpg width="256" height="192"]] || [[image:hersheykissafter.jpg width="253" height="189"]] || The wire was wrapped around him pretty tightly. The passenger was severely injured because the wire sliced through his arms and chest. It is clearly the thin dense material that did this || 1 ||
 * Yarn || [[image:bj_string_one.jpg width="256" height="192"]] || [[image:bj_string_twozel.jpg width="256" height="192"]] || Our observation of the string seat belt is that when the accident occurred, the figure slammed forward. This shows that the string is not sturdy enough to prevent an injury in an accident || 5 ||
 * String || [[image:stringlapoop.jpg width="256" height="192"]] || [[image:stringlapoop2.jpg width="256" height="192"]] || Our seatbelt made of string went around the chest. After going down the ramp, our passenger was still in the cart without any injuries. || 2 ||
 * Ribbon || [[image:panso_x3_ribbon.jpg width="256" height="192"]] || [[image:panso_ribbon_x4.jpg width="256" height="192"]] || We made a seatbelt out of ribbon that went around his waist shoulders and chest. When the cart went down the ramp, the seatbelt held him in place and the clay person didn't leave the cart. || 3 ||
 * tape || [[image:mitchel_lalalal_masking.jpg width="256" height="192"]] || [[image:michell_lalal_2_masking.jpg width="256" height="192"]] || we took a piece of tape and folded it over so there was no sticky part. We then twirled the end to make tying it easier. We put the tape belt around "her" waist and tied it around the bottom of the cart. Despite my face in the after picture, the tape actually worked well because our figure was unharmed and barely moved. || 4 ||

//** *Read the Physics Talk p268 - 271 before answering the following questions. * **// Questions:
 * 1) Define the terms: inertia, force and pressure. **(force: an interaction between two objects that can result in an acceleration of either or both objects; pressure: force per area where the force is normal [perpendicular] to the surface, measured in N/m^2 or Pa; inertia: the natural tendency of an object to remain at rest or to remain moving with constant speed in a straight)**
 * 2) In the collision, the car stops abruptly. What happens to the “passenger”? **(the passenger is launched forward)**
 * 3) What parts of your passenger were in greatest danger (most damaged)? **(the whole body is endangered: the body stops, but the heart, the brain, and other organs keep moving. The body wall exerts the force that brings the organs to rest)**
 * 4) What does Newton’s first law have to do with this? **(1st law: object in motion/rest will remain in motion/rest unless acted upon by an unbalanced force)**
 * 5) What materials were most effective as seatbelts? Why? **(ribbon, non-sticky tape)**
 * 6) Use Newton's first law of motion to describe the three collisions. **(1: [crashes] car has the collision & whatever it is exerts a force that makes the car stop. 2: [external body- seatbelt stop body] the car stops and the body keeps moving. the car exerts a force that makes the body stop its motion forward. 3: [internal body- ligaments and tendons stop organs] the body stops, but the heart, brain, and other organs keep moving; the body wall gives off a force that makes the body stop) --- 3 is most dangerous**
 * 7) Why does a broad band of material work better as a seatbelt than a narrow wire? **(all the force is spread out over a much larger area of contact)**

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. · Explain at least 1 cause of experimental error. Be sure you describe a specific reason. **(the clay is easily molded so the wire could have cut into the "passenger" before he was even sent down the ramp; everyone tied their passengers up differently and sent them down at different slopes)** · 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 change the material of the passenger because it is too easily molded. I would used a wooden figure that detaches at the joints because we would be able to touch it and it wouldn't look as though the passenger was injured)**
 * (an object in motion will remain in motion unless acted upon by an unbalanced force: in a collision the car stops but the passenger continues to move forward until a force acts upon him/her. That force is a seatbelt.**
 * Factors for effectiveness of a seatbelt: the material is broad, small pressure, limited stretch fabric**
 * For a race car driver, you would need a seatbelt that is tight, broad, and has a small pressure so an equal force is spread across the torso so the force will be too small to do any damage)**

Section 3

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


 * Hypothesis:** Respond to the objective fully. **An airbag is safer because our bodies are moving in a straight constant motion unless acted upon by an unbalanced force. the first force is a seatbelt, which is narrow. The Air bag is really protective because it is a large, wide force over a narrower surface, which is safer.**


 * Materials:** List any materials used and draw a labeled diagram of your set-up (alternatively, include a snapshot or video). **egg, flour, plastic bag, ruler, balance, bowl**


 * Procedure:**

**Note: //You may want to use the available technology to take "Before" and "After" pics to post in your data table to assist and elaborate on your written descriptions.//** // 1. Measure the height of your egg #1. =**.053 m** // // 2. Place an egg in a ziplock bag, squeezing out all of the air in the bag before sealing. // // 3. Hold a ruler up on the table vertically. Hold the egg vertically at the 2 cm mark. (Keep the excess bag on top.) Drop it. Record your observations. // // 4. Hold the egg the same exact way at the 4-cm mark and repeat. Continue this process until the egg shell is slightly cracked. // // 5. Continue until the egg is smashed and the yolk leaks out. Measure the amount of egg still undamaged. How much of the egg is smashed? Be sure to record detailed observations. // // 6. Fill a bowl with rice and place the bowl inside of the box lid. // // 7. Measure the height of your egg #2. = **.056 m ; mass: .059** // // 8. Drop the egg from the smash height (Step 3). Measure the amount of egg sticking up out of the rice bed. How much of the egg is buried in the rice? Also, record your observations. // // 9. Repeat this, increasing the height in 2-cm increments until the egg is cracked, and then smashed. //

//**Data and observations:** Add more columns/row as needed.//


 * **Egg #** || **Drop Height** || **Cracked or Smashed?** || **Description and Observations** || **Before** || **After** ||
 * 1 || **.02 m** || **stayed the same no cracks.** || **at 2cm the egg did not crack**
 * because it** **barley fell.** || [[image:giordanowikilog:Photo_66.jpg height="144" caption="Photo_66.jpg"]] || [[image:giordanowikilog:Photo_66.jpg height="144" caption="Photo_66.jpg"]] ||
 * 1 || **4 cm** || **got a little cracked at the bottom** || **the egg slightly cracked at the bottom when dropped at 4cm.** || [[image:giordanowikilog:Photo_66.jpg height="144" caption="Photo_66.jpg"]] || [[image:giordanowikilog:Photo_67.jpg height="144" caption="Photo_67.jpg"]] ||
 * 1 || **6 cm** || **more cracked** || **when dropped from 6 cm it cracked more** || [[image:giordanowikilog:Photo_67.jpg height="144" caption="Photo_67.jpg"]] || [[image:giordanowikilog:Photo_68.jpg height="144" caption="Photo_68.jpg"]] ||
 * 1 || **8 cm** || **cracked even more** || **when dropped from 8 cm the cracks where even worse** || [[image:giordanowikilog:Photo_68.jpg height="144" caption="Photo_68.jpg"]] || [[image:giordanowikilog:Photo_68.jpg height="144" caption="Photo_68.jpg"]] ||
 * 1 || **10 cm** || **crack even more than before** || **the egg is still cracked but we can see the yoke on the inside** || [[image:giordanowikilog:Photo_68.jpg height="144" caption="Photo_68.jpg"]] || [[image:giordanowikilog:Photo_69.jpg height="144" caption="Photo_69.jpg"]] ||
 * 1 || **12 cm** || **very cracked** || **yoke is starting to spill out the side** || [[image:giordanowikilog:Photo_69.jpg height="144" caption="Photo_69.jpg"]] || [[image:giordanowikilog:Photo_70.jpg height="144" caption="Photo_70.jpg"]] ||
 * 1 || **14 cm** || **smashed** || **at 14 cm the egg completely smashed and the yoke came out** || [[image:giordanowikilog:Photo_70.jpg height="144" caption="Photo_70.jpg"]] || [[image:giordanowikilog:Photo_71.jpg height="144" caption="Photo_71.jpg"]] ||
 * 2 || **14 cm** || **did not crack** || **The egg stayed in perfect condition. the egg is sticking out .037 meters and buried .019 m** || [[image:giordanowikilog:Photo_66.jpg height="144" caption="Photo_66.jpg"]] || [[image:giordanowikilog:Photo_72.jpg height="144" caption="Photo_72.jpg"]] ||
 * 2 || **18 cm** || **did not crack** || **The egg did not crack. it is sticking out .029 m and is buried .011 m.** || [[image:giordanowikilog:Photo_72.jpg height="144" caption="Photo_72.jpg"]] || [[image:giordanowikilog:Photo_72.jpg height="144" caption="Photo_72.jpg"]] ||
 * 2 || **22 cm** || **did not crack** || **the egg did not crack. it is sticking out .028 m and buried in .012 m.** || [[image:giordanowikilog:Photo_72.jpg height="144" caption="Photo_72.jpg"]] || [[image:giordanowikilog:Photo_72.jpg height="144" caption="Photo_72.jpg"]] ||
 * 2 || **28 cm** || **did not crack** || **the egg did not crack. it is sticking out .022 and is buried .018 m. This is with added flour to the bowl.** || [[image:giordanowikilog:Photo_72.jpg height="144" caption="Photo_72.jpg"]] || [[image:giordanowikilog:Photo_73.jpg height="144" caption="Photo_73.jpg"]] ||
 * 2 || **36 cm** || **did not crack** || **it is sticking out .018 meters and buried in .022 meters still without a crack.** || [[image:giordanowikilog:Photo_73.jpg height="144" caption="Photo_73.jpg"]] || [[image:giordanowikilog:Photo_73.jpg height="144" caption="Photo_73.jpg"]] ||
 * **2** || **45 cm** || **did not crack** || **it is sticking out .021 meters and buried in .019 meters still without a crack** || [[image:giordanowikilog:Photo_73.jpg height="144" caption="Photo_73.jpg"]] || [[image:giordanowikilog:Photo_73.jpg height="144" caption="Photo_73.jpg"]] ||
 * **2** || **60 cm** || **did not crack** || **it is sticking out .019 meters and buried in .021 meters still without a crack** || [[image:giordanowikilog:Photo_73.jpg height="144" caption="Photo_73.jpg"]] || [[image:giordanowikilog:Photo_73.jpg height="144" caption="Photo_73.jpg"]] ||
 * **2** || **90 cm** || **did not crack** || **it is sticking out .017 meters and buried in .023 meters still without a crack** || [[image:giordanowikilog:Photo_73.jpg height="144" caption="Photo_73.jpg"]] || [[image:giordanowikilog:Photo_73.jpg height="144" caption="Photo_73.jpg"]] ||
 * 2 || **from ceiling to floor** || **cracked!** || **from the ceiling the egg completely cracked and was sticking out .01 meters and buried .03 meters** || [[image:giordanowikilog:Photo_73.jpg height="144" caption="Photo_73.jpg"]] || [[image:giordanowikilog:Photo_74.jpg height="144" caption="Photo_74.jpg"]] ||


 * Calculations:** Show equation(s), numbers plugged in, and answer with correct units. Add columns in your data table to include these results.

mgh = GPE ; GPE = W (mgh = Fxd) ; F = W / d

** *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 rice represent?
 * 2) **the egg represents the person traveling in constant straight line motion in a car crash**
 * 3) **the table represents the windshield, dashboard, or hard surface in front**
 * 4) **the rice represents the airbag/cushion that acts as a non-dangerous unbalanced force**
 * 5) Define the terms: Kinetic Energy and Work.
 * 6) **kinetic energy**: the energy possessed by a moving body is called kinetic energy; KE = 1/2mv^2
 * 7) **work**: the amount of force applied on an object over a certain distance; W = F x d
 * 8) What factors determine an object's kinetic energy?
 * 9) **mass** (vehicle and its occupants)
 * 10) **velocity of the object** (velocity of vehicle)
 * 11) When work is done on an object, what is the effect on the object's kinetic energy?
 * 12) **Work can either increase the kinetic energy or decrease the kinetic energy depending on the direction of the applied force & the distance (displacement) that the object moves**
 * 13) How does the force needed to stop a moving object depend on the distance the force acts?
 * 14) **The object stopping the moving object needs to do Work and** W = d x F
 * 15) **greater the distance, lesser the force and vise-versa**
 * 16) What difference does a soft landing area make on a passenger during a collision?
 * 17) **the work done by a soft landing area decreases the kinetic energy of a person**
 * 18) **the KE of the person decreases and the energy of the soft landing increases**
 * 19) How does a cushion reduce the force needed to stop a passenger?
 * 20) **Cushions are able to protect a passenger by extending the distance it takes to stop him/her in an accident.**
 * 21) **the stopping distance is larger and the force required to stop the passenger is smaller**
 * 22) What does the law of conservation of energy have to do with this?
 * 23) **an object in motion will stay in motion unless acted upon by an unbalanced force. In this case, the object in motion is the person and the unbalanced force is the airbag protecting the person.**


 * Conclusion:**
 * Using the law of conservation of energy, explain how an air bag can protect you during an accident. Use specific observations from this investigation to support your answers to these questions.
 * **Because of the law of conservation of energy, a person in a car crash would stay in motion at constant speed unless stopped by an unbalanced force, which would be a hard windshield or dashboard. The hard surface would have to do work in order to stop the person and because the distance the person hits the surface is short, the force would be large. In order to decrease that large force, airbags increase the distance. (for lab substitute table for dashboard/hard surface, flour for airbag, and egg for person)**
 * Explain at least 1 cause of experimental error. Be sure you describe a specific reason.
 * **An experimental error would be due to the fact that flour changes its position in every trial and becomes compact. Therefore, the distance the egg was buried constantly changed and would decrease the distance by compacting to the bottom of the bowl.**
 * 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 improve the results by changing the flour. Instead, I would use a puffy, inflated material like an airbag that has pretty consistent size/position and doesn't stay compacted/patted down.**

Section 5
PTG 1. The automobile that has more momentum due to its velocity would push the stopped car forward so it gain velocity to the speed it was going. The already-moving car would stop. 4. They want heavier men, because they have a higher mass. The higher the momentum, the stronger and more forceful it will be in a collision (tackle) with a lighter player. The smaller guys don't have much of an impact on the bigger guys. 5. In a head on collision, the automobile with less momentum would get knocked backward. 6. P = mv 1000(10) = 10000 kg(m/s) 10000=10000v v = 1 m/s

**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). two carts, track, motion detector, masses

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 Bullet Cart m/s(kg) || Final Momentum Both carts m/s(kg) || Initial Momentum Target Cart || Sum Initial Momentum Both ||
 * .498 || .501 || .62 || 0 || .999 || .28 || .31 || .28 || 0 || .31 ||
 * .498 || .9993 || .47 || 0 || 1.4973 || .14 || .23 || .21 || 0 || .23 ||
 * .9963 || .501 || .43 || 0 || 1.4973 || .14 || .43 || .21 || 0 || .43 ||
 * .995 || .9993 || .47 || 0 || 1.9943 || .18 || .47 || .36 || 0 || .47 ||
 * .995 || 1.2493 || .55 || 0 || 2.2443 || .23 || .55 || .52 || 0 || .55 ||


 * Calculations:** Show equation(s), numbers plugged in, and answer with correct units. Add columns in your data table to include these results.
 * 1) Find the initial momentum of the bullet cart for each trial.
 * 2) **P=mv**
 * 3) **P = (.498 kg)(.62 m/s)**
 * 4) **P = .31 m/s(kg**)
 * 5) Find the initial momentum of the target cart for each trial.
 * 6) **P=mv**
 * 7) **P=(.501kg)(0m/s)**
 * 8) **P = 0 kg(m/s)**
 * 9) Find the sum of the initial momenta of the two carts for each trial.
 * 10) **initial momentum of Bullet Cart**
 * 11) Find the final momentum of the combined carts for each trial.
 * 12) **P = mv**
 * 13) **P = (.999kg)(.28m/s)**
 * 14) **P = .28 kg(m/s)**

** *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) **Except for the third trial, in all of the tests, the initial and final momentum were practically the same.**
 * 3) List the 6 types of collisions (top of page 312) and a brief description.
 * 4) **One moving object hits a stationary object and both stick together and move off at the same speed.**
 * 5) **Two stationary objects explode by the release of a spring between them and move off in opp. directions**
 * 6) **one moving object hits a stationary object. the first object stops, and the second object moves off**
 * 7) **one moving object hits a stationary object, and both move off at different speeds.**
 * 8) **two moving objects collide, and both objects move at different speeds after the collision**
 * 9) **two moving objects stick together and move off at the same speed**
 * 10) Which types of collisions are definitely inelastic? How do you know?
 * 11) **an inelastic collision is one where objects do not bounce off if each other, but rather move off together. Types 1 and 6 are inelastic.**
 * 12) Which types of collisions are definitely elastic? How do you know?
 * 13) **an elastic collision is one where objects bounce off of each other. Types 2, 4, and 5 are definitely elastic.**
 * 14) Define the law of conservation of momentum.
 * 15) **the total momentum before a collision is equal to the total momentum after the collision if no external forces act on the system.**
 * 16) 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.
 * 17) **the sum of the momentum of all the balls right after the collision is equal to the momentum of the original cue ball. This is because nature conserves momentum.** **The objects may move in new directions and with new speeds, but the momentum stays the same.**


 * 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 the investigators know the masses and velocities (momentum) of the vehicles before the collision, they can accurately display the masses and velocities (momentum) after the collision.**
 * **conserve means to maintain. By conserving momentum, the vehicles have the same momentum before & after a collision.**
 * Explain at least 1 cause of experimental error. Be sure you describe a specific reason.
 * **the flat track that the carts were being pushed around on was on a slight incline due to uneven materials on the bottom of the track. This could have offset the velocity, which is a key factor in calculating momentum.**
 * 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 improve the results of this lab by using a track the was fully flat to the table with no incline. That way, the target cart would stay still on its own and the velocities would be more accurate.**

PTG 2. X--> <--X <--XX-->

2a. p=mv Cart A: =(1)(2) = 2 kg (m/s)  Cart B = (1)(-2) = -2 kg (m/s)

2b. momentum before mvi + m2vi2 = P before (1kg)(2m/s) + (1kg)(-2m/s) 0 = Pbefore 2c. momentum after mvi + m2vi2 = mvf + m2vf2 (1kg)(2m/s) + (1kg)(-2m/s) = (1kg)(vf) + (1kg)(Vf2) 0 = 2kg(vf) 0 = Vf..... finally velocity of both carts is zero total momentum after the collision = 0.

3. mvi + m2vi2 = mvf + m2vf2 mVi + 0 = m(4) + m(4) mVi = 8m vi= 8 m/s

5. After they collide, vehicle B gains momentum (the 4000 kg(m/s) that vehicle A lost. The change in momentum of the system is zero because although A loses momentum, it is transferred to B.

6. mvi + m2vi2 = mvf + m2vf (2000kg)(3m/s) + (2000kg)(2m/s) = 2000Vf + 2000Vf 10000 = 4000 Vf 2.5 m/s = Vf

7. mvi + m2vi2 = mvf + m2vf2 80kg(10m/s) + (100kg)(8m/s) = 80kg(Vf) + (100kg)(9.78m/s) 622 = 80Vf 7.8 m/s = Vf

8. mvi + m2vi2 = mvf + m2vf2 (3)(2) + (1)(-2) = (3)(0) + (1)(Vf) 4 m/s = Vf2

Section 7
F = ma F = m (delta V / t) F x t = delta V x m

area on a force x time graph --> impulse if you know the area, that gives you the change in momentum

PTG

4. You bend your knees when you jump to the ground so they act as a crumple zone. The bending decreases the force by increasing the distance, so you slow down. Otherwise, the impact would be strong enough to break your legs.

6a. m=1200 kg, Vi = 10 m/s F x t = m x deltaV Ft = 1200(0-10) -12,000 kg(m/s) to bring it to rest

6b. Ft = 1200(5-10) Ft = -60000 -60,000 kg(m/s) to slow it down to 5 m/s

7a. F = 10,000N, t = 1.2 s F x t = J  10,000 x 1.2 = 12,000 N(s)

7b. Ft = m(deltaV) 12,000 = 1200(deltaV) 10 m/s is the change in velocity

8. J = p F x t = mv  F(.1) = 1500(-5) F = -75,000 N

10. The area of the first force x time graph is larger. The greater the area, the greater the impulse, or change in momentum. The bigger area is also a more dangerous collision.