Ch3_EisenbergAmandaE

= = toc =Section 1 =

Newspaper Source: The Record, January 19, 2010 The article includes a picture of cars driving on route 4, and it discusses the problems drivers have been facing from the snow and ice storms. The article says that "several cars spun out, and fender benders punctuated the morning rush." Mass transit delays and slick roads were the main concerns of commuters, along with the obvious black ice and slush.

What Do You See? A crash dummy family is sitting in a wrecked car. It stimulates what happened to the car when the airbag absorbs the impact from the cement wall.

What Do You Think? By wearing a seatbelt, you can protect yourself in a car. Airbags can also protect you in the case of a severe accident. Usually cars come equipped with safety measures to increase chances of survival.

Investigate 1)  2A) Novice Analyst: Some seem obvious while others are just a guess. 9 out of 15 based on prior knowledge is pretty decent.

3) (yes/no) || New Cars (1,2,3) ||
 * ** Safety features ** || Means of protection || Pre-1960 cars
 * seat belts || To keep people from flying through the window like a projectile. || No || 1 ||
 * head restraints || When your head is snapped back from the impact, the head restraint holds your head back, just like in a roller coaster. || No || 1 ||
 * front airbags || The airbag keeps you from flying into the windshield. || No || 1 ||
 * back up sensing system || It's an option available in many new cars that allows the driver to hear a beeping noise when there is an object in your blind spot when backing up. || No || 3 ||
 * front crumple zones || When you crash, the car folds up like an accordion and is shock absorbent, protecting the passengers inside. || No || 1, 2 ||
 * rear crumple zones || Increase collision distance reducing impact || No || 2 ||
 * side-impact beams in doors || Resists side penetration || No || 2 ||
 * shoulder belts for all seats || Keeps passengers in seats during collision || No || 1 ||
 * anti-lock braking systems (ABS) || Helps avoid skidding in the case that the car loses friction || No || 2 ||
 * tempered shatterproof glass || Helps prevent cuts || Yes || 1 ||
 * side airbags || They help you avoid being slammed in the car doors || No || 2 ||
 * turn signals || Turn signals allow the other drivers to see where you are going in order to avoid an accident. || Yes || 1 ||
 * electronic stability control || Helps resists rollovers || No || 2, 3 ||
 * energy-absorbing collapsible steering column || Prevents chest trauma || No || 1 ||

Physics Talk, p263
 * 1965: Ralph Nader wrote // Unsafe at Any Speed //
 * Looked at how safety was not a major consideration for the automobile industry
 *  Since then, the industry has made a 180 in safety
 * An Australian study found the following:
 * The incidence of fatal accidents involving 4WD Vehicles increased by 85% between 1990 and 1998
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Due to the growing number of kilometers the car was driven or that the safety features protect the driver 100%.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Incidence of fatal crashes decreased by 25% between 1990 and 1998

Checking Up <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">1) They added seat-belts, created collapsible steering columns and anti-lock brakes (ABS). <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">2) The incidence of fatal accidents involving 4WD Vehicles increased by 85% between 1990 and 1998 and in the incidence of fatal crashes decreased by 25% between 1990 and 1998.

What Do You Think Now? <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">By using the safety measure provided for you, your increase of survival sky rockets. However, the simplest way to avoid getting into an accident is to drive slowly and cautiously.

Physics To Go, p265 <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; margin: 0px; padding: 0px;">1) <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">2) A helmet, knee pads, wrist pads, bicycle brakes, a well oiled chain, and tires that have the right amount of air in them with treads for traction. <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; margin: 0px; padding: 0px;">3) A helmet, <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">knee pads, wrist pads, a back stop brake, and hard plastic as a cast to protect your ankles from breaking. <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; margin: 0px; padding: 0px;">4) A helmet, <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">knee pads, wrist pads, and wheels that have traction.
 * ** Safety features ** || F. R. S. T. ||
 * seat belts || F ||
 * head restraints || R ||
 * front airbags || F ||
 * front crumple zones || F ||
 * rear crumple zones || R ||
 * side-impact beams in doors || S ||
 * shoulder belts for all seats || F ||
 * side airbags || S ||
 * electronic stability control || T ||
 * energy-absorbing collapsible steering column || F ||

=<span style="font-size: 1.4em; margin: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 5px;">**Section 2** = <span style="font-size: 16px; line-height: 24px; margin: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 5px;">Investigate <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**Objectives & Hypothesis:**
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">What happens to a passenger involved in a car accident without and with a seatbelt?
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">When a passenger is not wearing a seatbelt, they become a projectile in the case of a head on collision. When they are wearing a seatbelt, they avoid flying through the windshield.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">What factors affect the passenger’s safety after a collision?
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Seat belts that are secured, and working airbags.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">How would a seat belt for a race car be different from one available on a regular car?
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">The seat belt needs to be more complex to keep the passenger in the car, especially because of the extremely high speeds the car is traveling at.

<span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**Hypothesis:**
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">I believe that our makeshift thread seatbelt will not keep the clay person in the vehicle, causing him to fly out like a projectile.

<span style="color: #800080; font-family: Arial,Helvetica,sans-serif;"> **Materials:** Clay, thread, tape, ramp, books, meter stick, and car.

<span style="color: #800080; font-family: Arial,Helvetica,sans-serif;"> **Procedure:**
 * 1) <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Make a clay figure and then place the figure in the cart.
 * 2) <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Arrange a ramp so that the endstop is at the bottom of the ramp.
 * 3) <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Adjust the height of the ramp to make a very shallow incline.
 * 4) <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Send the cart down the ramp.
 * 5) <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Very gradually increase the height of the ramp until significant “injury” happens to your figure. Make a note of this height.
 * 6) <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Fix your clay figure. Create a seatbelt for the figure and take a "Before" picture and post in your data table.
 * 7) <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">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) <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Repeat Steps 6 and 7, using different types of material for the seatbelt.

<span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**Data and observations:** <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;"> Injury Height with no seatbelt: 0.27 m Before (no seat belt)

After (no seat belt) [head crushed] Injury Height with no seatbelt: .27 m

through his body and sliced his neck. He also experienced severe head trauma; his head was crushed as seen in the picture above. || 6 ||
 * **//Type of Seatbelt//** || //**Before Picture**// || //**After Picture**// || //**Description and Observations**// || //**Group**// ||
 * Thread || [[image:woods-wiki:111Photo_45.jpg height="109" caption="111Photo_45.jpg"]] || [[image:woods-wiki:111Photo_46.jpg height="95" caption="111Photo_46.jpg"]] || Arm chopped off. The seat belt cut
 * Wire ||  || [[image:proringer:hershey_kissboybefore.jpg height="111" caption="hershey_kissboybefore.jpg"]] ||
 * hershey_kissboybefore.jpg ||  ||   || [[image:proringer:hersheykissafter.jpg height="109" caption="hersheykissafter.jpg"]] ||
 * hersheykissafter.jpg ||  ||   || **The wire was put around the passenger pretty tightly in order for him to stay on the cart after the collision. The wire was so tight that it sliced his arms and chest. The wire material is not a good idea because it can harm the person even if the collision wasnt that bad.** ||   || 1 ||
 * Yarn || [[image:activephysics-pvrhsd:sgrant22221.jpg height="140" caption="sgrant22221.jpg"]] ||  || [[image:activephysics-pvrhsd:sgrant11.jpg height="140" caption="sgrant11.jpg"]] ||
 * sgrant11.jpg ||  || Our observation of the yarn seat belt is that when the accident occurred, the figure slammed forward. This shows that the yarn is not sturdy enough to prevent an injury in an accident. || 7? ||
 * String ||  || [[image:activephysics-pvrhsd:stringgPhoto_86.jpg height="180" caption="stringgPhoto_86.jpg"]] ||
 * stringgPhoto_86.jpg ||  ||   || [[image:activephysics-pvrhsd:strringgPhoto_87.jpg height="180" caption="strringgPhoto_87.jpg"]] ||
 * strringgPhoto_87.jpg ||  || 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:activephysics-pvrhsd:Photo_38lp.jpg height="120" caption="Photo_38lp.jpg"]] ||
 * Photo_38lp.jpg ||  ||   || [[image:activephysics-pvrhsd:Photo_41lp.jpg height="140" caption="Photo_41lp.jpg"]] ||
 * Photo_41lp.jpg ||  || <span style="font: normal normal normal 13px/15px Arial; margin: 0px;">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:activephysics-pvrhsd:Photo_7758.jpg height="180" caption="Photo_7758.jpg"]] ||
 * Photo_7758.jpg ||  ||   || [[image:activephysics-pvrhsd:Photo_7662.jpg height="180" caption="Photo_7662.jpg"]] ||
 * Photo_7662.jpg ||  || 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 ||

<span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**Questions:** <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">1) Define the terms: inertia, force and pressure. <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">2) In the collision, the car stops abruptly. What happens to the “passenger”? 3) What parts of your passenger were in greatest danger (most damaged)? <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">4) What does Newton’s first law have to do with this? <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">5) What materials were most effective as seatbelts? Why? <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">6) Use Newton's first law of motion to describe the three collisions. <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">7) Why does a broad band of material work better as a seatbelt than a narrow wire?
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**Inertia:** The natural tendency of an object to remain at rest or to remain moving with constant speed in a straight line.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**Force:** An interaction between two objects that result in an acceleration of either or both objects
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**Pressure:** Force per area where the force is normal (perpendicular) to the surface; measured in N/m^2 or Pa (pascals)
 * The passenger flew out of the vehicle because our thread seatbelt was unable to keep him inside the car.
 * Our perso<span style="font-family: Arial,Helvetica,sans-serif;">n lost his hand at one point, as well as damaged his head multiple times.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Our person kept going down the ramp until something interacted with him and caused him to stop.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Ribbon and tape were the most effective because they were thicker and had more surface area to hold their clay models in the vehicle.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">A car hits an object (things in it keep moving)
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Person hits seatbelt of car (organs keep moving)
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Organs hit inside bone and ligaments
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">The narrow wire can cut into him during the impact rather than stabilize them in the case of an accident.

<span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**Conclusion:** <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">1) 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. <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">2) Explain at least 1 cause of experimental error. Be sure you describe a specific reason. <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">3) 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?)
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">The seatbelt keeps the person in the car and avoids being thrown into the windshield like a projectile. The width of the seatbelt and correct use of the shoulder strap allow the effectiveness of the seatbelt to be maximized. Based on the model from our experiment, you can see what happens when the seatbelt is too thin and does not exert enough force upon its user. When designing a seatbelt for a race car driver, I would make it similar to the ones found on a rollercoaster because the speeds are similar and allow maximum protection.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">Experimental error be described as our seatbelt maybe working once really well, but the other times it didn't work. That first trial could have been our example of experimental error.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">We would use a thicker seatbelt instead of thread. Although we wrapped the thread around him several times around his waist and then over his shoulder, it did not nearly exert the amount of force necessary to keep him from experiencing severe head trauma.

=<span style="font-size: 1.4em; margin: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 5px;">**Section 3** =

Investigation **Objective:** How does an air bag protect you during an accident?
 * It slows you down before hitting the dashboard so that your organs don't smash into the inside of you.

**Hypothesis****:** Air bags that have room for the air to move around allow for the safest protection.

**Materials:** Bag, meter stick, egg(s), flour, bowl

**Procedure:** 1. Measure the height of your egg #1. 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. 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 1: 0.075 kg & 0.053 m


 * **Egg #** || **Drop Height** || **Cracked or Smashed?** || **Description and Observations** || **How Deep** ||
 * 1 || .02 m || very small crack || no visible crack but audible one ||  ||
 * 1 || .04 m || small crack || visible and audible crack ||  ||
 * 1 || .06 m || crack || visible, audible crack. Barely any liquid seeping out ||  ||
 * 1 || .08 m || crack || hole in egg (membrane somewhat intact) ||  ||
 * 1 || .1 m || bad crack || top flattened (liquid everywhere. no yoke yet) ||  ||
 * 1 || .12 m || badder crack || everything is getting worse ||  ||
 * 1 || .14 m || baddest crack || almost done ||  ||
 * 1 || .16 m || awful crack || yoke isn't out (but things are bad) ||  ||
 * 1 || .18 m || smashed || total annihilation ||  ||
 * 2 || .18 m || perfect || nothing changed || .016 m ||
 * 2 || .2 m || perfect || nothing changed || .026 m ||
 * 2 || .24 m || no crack || nothing happened || .031 m ||
 * 2 || .28 m || no crack || nothing happened || .033 m ||
 * 2 || .32 m || no crack || nothing happened || .035 m ||
 * 2 || .36 m || no crack || nothing happened || .036 m ||
 * 2 || .4 m || no crack || nothing || .037 m ||
 * 2 || .44 m || no crack || nothing || .036 m ||
 * 2 || .5 m || no crack || nothing || .037 m ||
 * 2 || .6 m || no crack || nothing || .04 m ||
 * 2 || .7 m || no crack || nothing || .037 m ||
 * 2 || .8 m || no crack || nothing || .036 m ||
 * 2 || 3 m || CRACK || CRACK || .045 m ||

Egg 1 (after accident): 0.041 m

Calculations: Show equation(s), numbers plugged in, and answer with correct units. Add columns in your data table to include these results. GPE = mgh GPE = W W = FD  **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) Define the terms: Kinetic Energy and Work. 3) What factors determine an object's kinetic energy? 4) When work is done on an object, what is the effect on the object's kinetic energy? 5) How does the force needed to stop a moving object depend on the distance the force acts? 6) What difference does a soft landing area make on a passenger during a collision? 7) How does a cushion reduce the force needed to stop a passenger? 8) What does the law of conservation of energy have to do with this?
 * What is the gravitational potential energy in each trial?
 * How much work is done in each trial?
 * How much force was used to stop the egg in each case of steps 5, 8 and 9.
 * W (J) || F (N) || D (m) ||
 * .106 || 6.625 || .016 ||
 * .118 || 4.54 || .026 ||
 * .141 || 4.55 || .031 ||
 * .165 || 5 || .033 ||
 * .188 || 5.37 || .035 ||
 * .212 || 5.89 || .036 ||
 * .235 || 6.35 || .037 ||
 * .259 || 7.19 || .036 ||
 * .294 || 7.95 || .037 ||
 * .353 || 8.825 || .04 ||
 * .412 || 11.14 || .037 ||
 * 1.764 || 39.2 || .045 ||
 * The egg represents a person whereas the bag acts as an airbag. It protects the body from the force due to a collision, as seen by the flour. The flour shows the exact impact, and the chart shows the distance the egg was dropped, its impact, and the damage done to the egg.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**Kinetic Energy:** the energy possessed by a moving body is called kinetic energy. KE = 1/2(m)(v^2)
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**Work:** the amount of force applied on an object over a distance; W = Fd
 * Mass and velocity effect an object's kinetic energy.
 * When the force and distance are increased, so does the object's kinetic energy. The same goes for the decreasing work.
 * 1/2m(v^2) = fd
 * The force needs to increase to stop a moving object when the distance decreases.
 * The person is able to absorb the shock better if the landing area is soft
 * The cushion allows the body to move into the cushion (as shown in the video) and absorbs the impact.
 * It changes the amount of force over a distance of time.

>>
 * 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 all of the energy from the forward momentum is countered by acting on something to stop it, more force needs to be applied. Air bags increase the distance slowing down and decrease the force.
 * Explain at least 1 cause of experimental error. Be sure you describe a specific reason.
 * Flours and egg cannot accurately parallel a person flying into a dashboard, and it does not show its effectiveness towards the human anatomy.
 * 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?)
 * You can redo the test and see how fast a head will become injured without an airbag and compare the results.

= = = = =<span style="font-size: 1.4em; margin: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 5px;"> Section 5 = ** Investigation ** **See Group Wiki**

<span style="font-size: 1.4em; margin: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 5px;">** Physics Talk ** <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; margin: 0px; padding: 0px;">**Momentum:** quantity of motion described by the product of mass and velocity
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">mass x velocity
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Large mass, small velocity
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Small mass, large velocity
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Large mass, large velocity

** Physics To Go ** <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**1)** Because the mass is equal and car #2 has velocity, the second car has much more momentum and damages car #1. <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**4)** Those players have more mass, which means that it's harder to get through to the quarterback. Plus, the linemen have more momentum once they start going, which results in a harder hit. <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**5)** The smaller car will get hit with the biggest impact due to its smaller mass in comparison to the large truck <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**6)** mass x velocity = mass x velocity <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">1,000 x 10 = 10,000 x v <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">10,000 = 10,000(v) <span style="color: #800080; font-family: Arial,Helvetica,sans-serif;">**v = 1 m/s**

= = =<span style="font-size: 1.4em; margin: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 5px;"> Section 6 = <span style="font-size: 1.4em; margin: 0px; padding-bottom: 0px; padding-left: 0px; padding-right: 0px; padding-top: 5px;">** Investigation ** Objective: What physics principles do the traffic-accident investigators use to "reconstruct" the accident?
 * They look at the mass and velocity of the objects involved in the investigation and use those numbers.

Materials: Ramp, motion detector, and 2 carts

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)** ||
 * 0.505 || 0.489 || 0.34 || 0 || 0.994 || 0.18 ||
 * 0.755 || 0.489 || 0.41 || 0 || 1.244 || 0.25 ||
 * 1.003 || 0.489 || 0.39 || 0 || 1.492 || 0.28 ||
 * 0.505 || 0.739 || 0.42 || 0 || 1.244 || 0.2 ||
 * 1.005 || 0.949 || 0.52 || 0 || 1.954 || 0.29 ||

(mass1 + mass2) || Final Momentum (mass x velocity) 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.
 * Momentum of Bullet Cart (mass x velocity) kg*m/s || Momentum of Target Cart (mass x velocity) kg*m/s || Sums of Initial Momenta
 * 0.505(0.34) = 0.1717 || 0.489(0) = 0 || 0.1717 || 0.994(0.18) = 0.1789 ||
 * 0.755(0.41) = 0.3096 || 0.489(0) = 0 || 0.3096 || 1.224(0.25) = 0.306 ||
 * 1.003(0.39) = 0.3912 || 0.489(0) = 0 || 0.3912 || 1.492(0.28) = 0.4178 ||
 * 0.505(0.42) = 0.2121 || 0.739(0) = 0 || 0.2121 || 1.244(0.2) = 0.2488 ||
 * 1.005(0.52) = 0.5226 || 0.949(0) = 0 || 0.5226 || 1.954(0.29) = 0.5667 ||

1) Compare the initial momenta (calc 3) to the final momentum (calc 4). (Allow for minor variations due to uncertainties of measurement.) 2) List the 6 types of collisions (top of page 312) and a brief description. 3) Which types of collisions are definitely inelastic? How do you know? 4) Which types of collisions are definitely elastic? How do you know? 5) Define the law of conservation of momentum. 6) 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.
 * Questions:**
 * The two calculations are surprisingly pretty close to one another. The initial momenta is a little smaller than the final momentum, but not by much.
 * A moving object hits a non-moving object and they move together at the same speed
 * Two objects spring away from one another
 * A moving object hits a non-moving object and transfers all of its momentum to the stationary one
 * A moving object hits a stationary object and they bounce off at different speeds
 * Two objects hit one another and go off at different speeds
 * Two objects hit and move at the same speed
 * Types 2, 4, and 5 are all kinetic energy and therefore are not elastic.
 * Types 1, 3, and 6 do not show a change in kinetic energy, which makes them elastic.
 * **Law of Conservation of Momentum:** the total momentum before a collision is equal to the total momentum after the collision if no external forces act on the system.
 * The stick hits the cue ball quickly, and that momentum is transferred onto the first ball it hits. That ball hits the rest of the triangle, and the balls' velocities are then slower as a result of the momentum being shared through all of the balls.

1) 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? 2) Explain at least 1 cause of experimental error. Be sure you describe a specific reason. 3) 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?)
 * Conclusion:**
 * Investigators are able to look how how the momentum was transferred between cars and decide who is to blame.
 * Weather conditions could be of experimental error, as they alter speeds.
 * I would actually add elements to make the ramp slick to see if that changed the velocity or momentum of the car.

** Physics to Go ** ** 2A) Cart 1 ** p = mv  p = 1(2)  p = 2 kg*m/s  **Cart 2**  p = mv  p = 1(-2)  p = -2 kg*m/s  2B) p(total) = p(cart 1) + p(cart 2) p = 2 - 2 **p = 0 kg*m/s** 2C) P(total) = P(cart 1) + P(cart 2) P = -2 + 2  **P = 0 kg*m/s**  3) p(car 1) + p(car 2) = 4 m/s (2m) mv(car 1) + mv(car 2) = 4 m/s (2m) v(car 1) + v(car 2) = 8 m/s v(car 1) + 0 = 8 m/s **v(car 1) = 8 m/s** 5) 4,000 kg*m/s and a total change of 0 kg*m/s during the collision because car A gives all of its momentum to car B. 6) p(cart 1) + p(cart 2) = p(total) mv(cart 1) + mv(cart 2) = mv (total) 2000(3) + (2000)(2) = (4000)(v) **v = 2.5 m/s** 7) p(player 1) + p(player 2) = p(player 1) + p(player 2) mv(player 1) + mv(player 2) = mv (player 1) + mv (player 2)  80(10) + 100(8) = 80(v) + 100(9.78)  **7.8 m/s = v in same direction**  8) p(ball 1) + p(ball 2) = p(ball 1) + p(ball 2) mv(ball 1) + mv(ball 2) = mv (ball 1) + mv (ball 2) 3(2) + 1(-2) = 3(0) + 1(v) **v = 4 m/s**

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