Chapter+3

= = toc Chapter 3: Safety

Chapter 3 Section 1
What do You see?
 * Test Dummies going through car crash
 * Car is crashing into a barricade
 * Crashing simulation

What do you Think?
 * How can you protect yourself from serious injury should an accident occur?
 * You can wear or equip your vehicle with safety material. This will stun the impact of the accident; thus, providing less injury

Investigate


 * Score: 9/15 (60%): Novice Analyst
 * I am not surprised with my knowledge considering the ones i answered correctly were more logical and straight-forward.

(yes/no) || New Cars (1,2,3) ||
 * Safety features || Means of protection || Pre-1960 cars
 * seat belts || To prevent you from being a projectile || No || All ||
 * head restraints || To prevent back-lash || No || All ||
 * front airbags || To prevent you from being a projectile || No || All ||
 * back up sensing system || To indicate if a car will hit something || No || Few ||
 * front crumple zones || To absorb the impact of a crash in the front || No || All, Some ||
 * rear crumple zones || To absorb the impact of a crash in the back || No || Some ||
 * side-impact beams in doors || Resists side penetration || No || Some ||
 * shoulder belts for all seats || Keeps passenger in seat during collision || No || All ||
 * anti-lock braking systems (ABS) || Helps maintain control, Prevents skid || No || Some ||
 * tempered shatterproof glass || Helps prevent Cuts || Yes || All ||
 * side airbags || Protects Head. Torso || No || Some ||
 * turn signals || Warns other drivers of actions || Yes || All ||
 * electronic stability control || Helps resist rollovers || No || Some, Few ||
 * energy-absorbing collapsible steering column || Prevent Chest Trauma || Yes || All ||

Physics Talk


 * Pedestrians can be injured by vehicles so Engineers try to build them to harm the pedestrian in the least
 * Safety was not always a concern, until Ralph Nader's book in 1965
 * Put Seat-belts
 * Removed Chrome Dashboards
 * Removed Solid Steering Column
 * Australian Study on 4WD
 * Accident Rate increased
 * Could be because of more 4WD cars
 * Or the assumption that they are a lot safer and people speed more with them

Checking Up

1. List three ways manufacturers have made vehicles safer since the 1960's? 2. What are two explanations for 4WD crashes
 * Put Seat-belts
 * Removed Chrome Dashboards
 * Removed Solid Steering Column
 * Increase in 4WD drivers
 * Increase in speed because of false information

What do you Think Now?

1. How can you protect yourself from serious injury should an accident occur?
 * In order to protect myself from injury I would purchase a vehicle with safety features such as seat belts, air bag, back head rest, (etc.). I believe the most effective tool out of all the safety harnesses is the seat belt, it keeps you in the seat and prevents you from being a projectile. Actions that will NOT protect me in an accident would be not wearing seat-belts, disabling airbags, and taking off the head rest, and many other things.

Physics To Go

1. Review all the safety features you learned and label them 2,3,4. Safety Features
 * F:
 * Seat-belts
 * Head Restraints
 * Front Airbags
 * Front Crumple Zone
 * (ABS)
 * Turn Signals
 * Shatterproof Glass
 * Collapsible steering column
 * R:
 * Seat-Belts
 * Head Restraints
 * Back Up System
 * Rear Crumple Zone
 * Turn Signals
 * S:
 * Side Impact Beam
 * Shatterproof Glass
 * Side Airbags
 * T:
 * Seat-belt
 * Shatterproof Glass
 * Side Airbags
 * Helmets
 * Elbow Pads
 * Knee Pads

Investigate X2: Newton's First Law and Seat belts
Objectives:


 * What happens to a passenger involved in a car accident without and with a seatbelt?
 * With: Seatbelt hold passenger back and stops inertia
 * Without: Car stops, inertia still acts on passenger and flings out the window
 * What factors affect the passenger’s safety after a collision?
 * Whether seat-belts are on or off
 * Airbags
 * Headrest
 * How would a seat belt for a race car be different from one available on a regular car?
 * It should be a lot stronger and able to resist more because the car is going faster

Hypothesis: Respond to each of the above objectives fully.

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.
 * 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.

through his body and sliced his neck. || 6 ||
 * Type of Seatbelt || Before Picture || After Picture || Description and Observations || Group ||
 * Thread || [[image:activephysics-pvrhsd:111Photo_45.jpg caption="111Photo_45.jpg"]] || [[image:activephysics-pvrhsd:111Photo_46.jpg caption="111Photo_46.jpg"]] || Arm chopped off. The seat belt cut
 * Wire || [[image:proringer:hersheykissafter.jpg caption="hersheykissafter.jpg"]] || [[image:proringer:hershey_kissboybefore.jpg caption="hershey_kissboybefore.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 caption="sgrant22221.jpg"]] || [[image:activephysics-pvrhsd:sgrant11.jpg caption="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. || 5 ||
 * String || [[image:activephysics-pvrhsd:stringgPhoto_86.jpg caption="stringgPhoto_86.jpg"]] || [[image:activephysics-pvrhsd:strringgPhoto_87.jpg caption="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 caption="Photo_38lp.jpg"]] || [[image:activephysics-pvrhsd:Photo_41lp.jpg caption="Photo_41lp.jpg"]] || 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 ||
 * 1-in masking || [[image:activephysics-pvrhsd:Photo_7758.jpg caption="Photo_7758.jpg"]] || [[image:activephysics-pvrhsd:Photo_7662.jpg caption="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? ||
 * String || [[image:activephysics-pvrhsd:stringgPhoto_86.jpg caption="stringgPhoto_86.jpg"]] || [[image:activephysics-pvrhsd:strringgPhoto_87.jpg caption="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 caption="Photo_38lp.jpg"]] || [[image:activephysics-pvrhsd:Photo_41lp.jpg caption="Photo_41lp.jpg"]] || 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 ||
 * 1-in masking || [[image:activephysics-pvrhsd:Photo_7758.jpg caption="Photo_7758.jpg"]] || [[image:activephysics-pvrhsd:Photo_7662.jpg caption="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? ||

Data and observations:


 * With string seatbelt, Clay dummy did not fling out of cart, but bent and hit his head on the front
 * Car stopped, but dummy kept moving until he hit something

Questions:
 * Read the Physics Talk p268 - 271 before answering the following questions. *
 * 1) Define the terms: inertia, force and pressure.
 * 2) Inertia - to remain unchanged until a force acts upon you
 * 3) Force- strength or energy as attribute to a physical action or movement
 * 4) Pressure- the continuous physical force exerted on or against an object by something in contact with it
 * 5) In the collision, the car stops abruptly. What happens to the “passenger”?
 * 6) He remains in inertia and keeps traveling until something stops him
 * 7) What parts of your passenger were in greatest danger (most damaged)?
 * 8) His head
 * 9) What does Newton’s first law have to do with this?
 * 10) An object in motion stays in motion unless a force is acted upon it, and the person kept traveling until something stopped him
 * 11) What materials were most effective as seatbelts? Why?
 * 12) Use Newton's first law of motion to describe the three collisions.
 * 13) Why does a broad band of material work better as a seatbelt than a narrow wire?

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. · 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?)
 * A seat belt is a very important safety feature because it stops your inertia after a car crash.
 * If the seat belt wasn't securely made
 * I would create a head rest on the cart to be able to make a better seat belt and make a more realistic scenario

Investigate X3: Energy and Air Bags
Objective:
 * How does an air bag protect you during an accident?

Hypothesis: Respond to the objective fully.

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

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. 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 # || Drop Height || Cracked or Smashed? || Description and Observations || Mass (kg) || Height of Egg After Drop (m) || Total Damage or Sinkage (m) ||
 * 1 || 2 cm. || The egg cracked. || The egg slightly cracked on the point of impact. || 0.055 || 0.060 || 0 ||
 * 1 || 4 cm. || The egg cracked. || The egg had a more severe crack at the point of impact. || 0.055 || 0.060 || 0 ||
 * 1 || 6 cm || The egg CRACKED || The egg became indented. || 0.055 || 0.058 || 0.002 ||
 * 1 || 8 cm. || THE EGG cracked.... || More indentation and cracks. || 0.055 || 0.056 || 0.004 ||
 * 1 || 10 cm || The egg cracked || The egg is in a cracked state. Most of the egg is cracked. || 0.055 || 0.056 || 0.004 ||
 * 1 || 12 cm || Cracked || The egg is still cracked and white oozed out || 0.055 || 0.055 || 0.005 ||
 * 1 || 14 cm || Severely cracked. || Cracked to the point of major oozing || 0.055 || 0.050 || 0.010 ||
 * 1 || 16 cm || Smashed || The yolk is completely out. || 0.055 || 0.045 || 0.015 ||
 * 1 Pt. 2 || 16 cm || No cracks at all. || The egg sank about 0.016 m. || 0.0564 || 0.040 || 0.016 ||
 * 1 Pt. 2 || 20 cm || No cracks at all. || The egg sank about 0.021 m. || 0.0564 || 0.035 || 0.021 ||
 * 1 Pt. 2 || 24 cm || No cracks at all. || The egg sank about 0.024 m || 0.0564 || 0.032 || 0.024 ||
 * 1 Pt. 2 || 28 cm || No cracks at all. || The egg sank about 0.025 m. || 0.0564 || 0.031 || 0.025 ||
 * 1 Pt. 2 || 2 m || No cracks || The egg sank about 0.028 m || 0.0564 || 0.028 || 0.028 ||
 * 1 Pt. 2 || 2.5 m || The egg finally cracked from an outrageous height. || The egg had cracks surrounding it. It exploded. It sank down right to the end of the plate about 0.030 m. || 0.0564 || 0.026 || 0.030 ||

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?

Part I:
 * Trial || GPE (mgh) || Answer (Joules) ||
 * 1 || (.055g)(9.8m/s sq.)(2cm) || 10.78 ||
 * 2 || (.055g)(9.8m/s sq.)(4cm) || 21.56 ||
 * 3 || (.055g)(9.8m/s sq.)(6cm) || 32.34 ||
 * 4 || (.055g)(9.8m/s sq.)(8cm) || 43.12 ||
 * 5 || (.055g)(9.8m/s sq.)(10cm) || 53.90 ||
 * 6 || (.055g)(9.8m/s sq.)(12cm) || 64.68 ||
 * 7 || (.055g)(9.8m/s sq.)(14cm) || 75.46 ||
 * 8 || (.055g)(9.8m/s sq.)(16cm) || 86.24 ||


 * Part II:

Trial || GPE (mgh) || Answer (Joules) ||
 * 1 || (.564g)(9.8 m/s sq.)(16cm) || 88.435 ||
 * 2 || (.564g)(9.8 m/s sq.)(20cm) || 110.544 ||
 * 3 || (.564g)(9.8 m/s sq.)(24cm) || 132.653 ||
 * 4 || (.564g)(9.8 m/s sq.)(28cm) || 154.762 ||
 * 5 || (.564g)(9.8 m/s sq.)(200cm) || 1,105.44 ||
 * 6 || (.564g)(9.8 m/s sq.)(250cm) || 1,381.80 ||


 * How much work is done in each trial?

Part I:
 * Trial || Work (F * d) || Answer (Joules) ||
 * 1 || (.539N)(2cm) || 1.078 ||
 * 2 || (.539N)(4cm) || 2.156 ||
 * 3 || (.539N)(6cm) || 3.234 ||
 * 4 || (.539N)(8cm) || 4.312 ||
 * 5 || (.539N)(10cm) || 5.390 ||
 * 6 || (.539N)(12cm) || 6.468 ||
 * 7 || (.539N)(14cm) || 7.546 ||
 * 8 || (.539N)(16cm) || 8.624 ||

Part II:


 * Trial || Work (F * d) || Answer (Joules) ||
 * 1 || (.553)(16cm) || 8.848 ||
 * 2 || (.553N)(20cm) || 11.06 ||
 * 3 || (.553N)(24cm) || 13.27 ||
 * 4 || (.553N)(28cm) || 15.48 ||
 * 5 || (.553N)(200cm) || 110.60 ||
 * 6 || (.553N)(250cm) || 138.25 ||


 * How much force was used to stop the egg in each case of steps 5, 8 and 9.
 * 0 force was used on the egg, we just dropped it from a certain height

Questions:
 * Read the Physics Talk p279 - 287 before answering the following 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?
 * The egg = human
 * Table = Collision Point
 * Rice = Air bag
 * 1) Define the terms: Kinetic Energy and Work.
 * Work - force times distance
 * Kinetic Energy - the energy an object has because of motion
 * 1) What factors determine an object's kinetic energy?
 * the mass and velocity of the object
 * 1) When work is done on an object, what is the effect on the object's kinetic energy?
 * it increases it
 * 1) How does the force needed to stop a moving object depend on the distance the force acts?
 * the larger the force the smaller the distance and vice versa.
 * 1) What difference does a soft landing area make on a passenger during a collision?
 * He/She is less likely to get injured and it will cushion their stop
 * 1) How does a cushion reduce the force needed to stop a passenger?
 * It absorbs some of the force needed to stop the passenger
 * 1) What does the law of conservation of energy have to do with this?
 * energy can neither be created or destroyed so the energy you have moving transfers into the collision

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 the energy during a collision is being transferred into the accident, an air bag puts the force into the airbag instead of somewhere more dangerous

· Explain at least 1 cause of experimental error. Be sure you describe a specific reason. - If we didnt precisely measure the dropping height · 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?) - We could have used a tape measure, it would be more precise the putting meter sticks together

Chapter 3 Section 4
Physics To Go 1)Because the mass is equal and car #2 has velocity, the second car has much more momentum and damages car #1. 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. 5)The smaller car will get hit with the biggest impact due to its smaller mass in comparison to the large truck 6)mass x velocity = mass x velocity
 * 1,000 x 10 = 10,000 x v
 * 10,000 = 10,000(v)
 * v = 1 m/s

Chapter 3 Section 6
Investigate X6: Momentum and Inelastic Collisions

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) ||
 * .502 || .494 || .57 || 0 || .996 || .27 ||
 * 1.002 || .494 || .47 || 0 || 1.496 || .25 ||
 * .502 || .994 || .56 || 0 || 1.496 || .19 ||
 * 1.002 || .994 || .36 || 0 || 1.996 || .14 ||
 * 1.502 || .494 || .43 || 0 || 1.996 || .24 ||

Calculations: Show equation(s), numbers plugged in, and answer with correct units. Add columns in your data table to include these results. >> 1. p = (.501)(.85)= 0.426 km(m/s) >> 2. p = (.726)(.84)=0.609 km(m/s) >> 3. p = (1)(.65)=0.65 km(m/s) >> 4. p = (1.25)(.79)=0.988 km(m/s) >> 5. p = (1.5)(.75)= 1.125 km(m/s) >> 6. p = (1)(.76)= .76 km(m/s) >> 1. p = (.499)(0)= 0 km(m/s) >> 2. p = (.499)(0)= 0 km(m/s) >> 3. p = (.499)(0)=0 km(m/s) >> 4. p = (.499)(0)= 0 km(m/s) >> 5. p = 1(0)=0 km(m/s) >> 6. p = 2(0)=0 km(m/s) >> 2. .609+0= .609 km(m/s) >> 3. .65+0= .65 km(m/s) >> 4. .988+0= .988 km(m/s) >> 5. 1.125+0= 1.125 km(m/s) >> 6. .76+0= .76 km(m/s) >> 1. p= (1.009)(.42)= 0.424 km(m/s) >> 2. p= (1.225)(.49)= 0.6002 km(m/s) >> 3. p= (1.499)(.5)= 0.7495 km(m/s) >> 4. p= (1.749)(.61)= 1.0669 km(m/s) >> 5. p= (2.5)(.45)= 1.125 km(m/s) >> 6. p= (3)(.31)= 0.93 km(m/s) >>
 * 1) Find the initial momentum of the bullet cart for each trial.
 * 2) p= mv
 * 1) Find the initial momentum of the target cart for each trial.
 * p=mv
 * 1) Find the sum of the initial momenta of the two carts for each trial.
 * 1. 0.426+0= .426 km(m/s)
 * 1) Find the final momentum of the combined carts for each trial.
 * p=mv

Questions:
 * Read the Physics Talk p312 - 315 before answering the following questions. *
 * 1) Compare the initial momenta (calc 3) to the final momentum (calc 4). (Allow for minor variations due to uncertainties of measurement.)
 * 2) All of them are very similar. They vary slightly because of small amounts of friction in that split second and faulty measurements.
 * 3) List the 6 types of collisions (top of page 312) and a brief description.
 * 4) Collision Type 1 - one object hits stationary object and they move together
 * 5) Collision Type 2 - Two Stationary objects explode by a release of a spring between them and move off in opposite directions
 * 6) Collision Type 3 - One moving object hits a stationary object. The first stops and second one moves on
 * 7) Collision Type 4 - One hits the other, both move at different speeds
 * 8) Collision Type 5 - Two objects collide, and both move at different speeds after the collision
 * 9) Collision Type 6 - Two objects collide, and both move off at
 * 10) Which types of collisions are definitely inelastic? How do you know?
 * 11) Types 2, 4, and 5 because they involve a change in KE
 * 12) Which types of collisions are definitely elastic? How do you know?
 * 13) Types 1, 3, and 6 because they don't have a change in KE
 * 14) Define the law of conservation of momentum.
 * 15) The total momentum before the collision = the total momentum after collision if no external force acts 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 momentum of the balls before they are hit by the cue ball is equal to the momentum after they are hit

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? · Explain at least 1 cause of experimental error. Be sure you describe a specific reason. 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?)
 * they can see how far the "target" car went and where the "bullet" car is and determine what happened that way through momentum and how much the cars weigh and who was at fault
 * a cause for experimental error could be misalignment of the wheels on the cart and the ramp. This can cause the cart to not travel at it's full potential
 * We would use better Velcro, because ours did not stick as well as it should have.

Physics To Go

2. Diagram of Carts 2a. Calculate the momentum of each cart before the collision
 * m1v1 + m2v2 =
 * 2 m/s + (-2 m/s) = 0

2b. Calculate the total momentum before the collision 2c. Calculate the total momentum after the collision 3. What was the speed of the vehicle before the collision? 5. Vehicle A and B collide and A loses 4000 kg * m/s of momentum. What is the change in momentum of Vehicle B. What is change in momentum due to collision? 6. What is the speed of the cars as they lock together? 7. What is the 80 kg players velocity 8. What is the velocity of the 1kg object after the collision? 9. 10. 11. 12. 13. 14. 1,200 kg
 * p = mv + mv
 * p = 2 kg * m/s + 2 kg * m/s
 * p = 4 kg * m/s
 * Same answer as 2b
 * mi1vi1 + mi2vi2 = m1vf1 + m2vf2
 * m(v1) = 8m
 * v1 = 8
 * v = 8 m/s
 * the momentum goes into the other cart
 * mi1vi1 + mi2vi2 = m1vf1 + m2vf2
 * 6000 + 4000 = 4000vf
 * 10000 = 4000vf
 * 2.5 m/s = vf
 * mi1vi1 + mi2vi2 = m1vf1 + m2vf2
 * 800 + 800 = 80vf +978
 * 1,600 = 80vf + 978
 * 622 = 80vf
 * 7/8 m/s = vf
 * mi1vi1 + mi2vi2 = m1vf1 + m2vf2
 * 6 - 2 = vf
 * +4m/s = vf
 * -12 m/s
 * m1v1 + m2v2 = mvf + m2vf
 * (7) - 1.8 = 3.5 + .06vf
 * 28.3 m/s = vf
 * -2 m/s
 * .05 m/s
 * 1.1 m/s