Chapter+3

=Chapter 3= toc

Section 1

 * __What do you see?__**

A car crash simulation going down at a testing facility. Dummies with center of masses marked. Things from inside the car flying out of it becoming projectiles. Things cushioning the dummies inside and keeping them safe. The test car was successful at keeping the passengers safe.


 * __What do you think?__**

I think you would definitely need something to bind you to your seat and also something else to cushion you if the binding breaks or you slip out of it. I think this is all that is required to keep someone safe in the event of an accident.


 * __Investigate__**

Part 1:

Part 2:

11/15, Assistant Analyst. These results did not surprise me.

Part 3:

(yes/no) || New Cars (1,2,3) || protecting the passengers. || no || 2 || Also keeps passenger safe from breaking through windshield. || yes || 1 || instead of windshield. || no || 2 || Allows for short term premonitions. || yes || 1 ||
 * ** Safety features ** || Means of protection || Pre-1960 cars
 * seat belt || Keeps lower torso stable. || no || 1 ||
 * head restraints || Keeps head stable. || no || 1 ||
 * front airbags || To stop the people from moving and hitting the steering wheel or the windshield. || no || 1 ||
 * back up sensing system || To alert you when something is very close to the back of your car. || no || 3 ||
 * front crumple zones || To redirect and absorb shock. || no || 1 ||
 * rear crumple zones || To redirect and absorb shock. || no || 1 ||
 * side-impact beams in doors || Makes door rigid, protects passenger from outside injury. || no || 1 ||
 * shoulder belts for all seats || Keeps upper torso stable. || no || 1 ||
 * anti-lock braking systems (ABS) || Prevents the car from skidding and turning over when making a turn,
 * tempered shatterproof glass || Keeps passenger safe from potential projectiles that could break through the glass.
 * side airbags || Same purpose as front airbags just from different side and the side windows
 * turn signals || Lets people around you know that your about to turn.
 * electronic stability control || Detects and minimizes skids. || no || 3 ||
 * energy-absorbing collapsible steering column || Prevents excessive injury to driver. || no || 1 ||

__**Summary of Physics Talk and** **Checking Up #'s 1 and 2**__

After Ralph Nader's book, Unsafe At Any Speed, was published the government and car companies began making and designing their cars to be safer. Not only to protect the driver and passengers but also to protect pedestrians that may get struck by the vehicle.

1. Since 1960, manufacturer's have installed seat belts, padded dashboards and collapsible steering columns.

2. Studies have shown that people with 4WD cars, which are safer cars, get into more accidents. The belief for this is that people take new safety features for granted and overcompensate on them and therefore get into more riskier situations and ultimately get hurt.

__**Physics To Go #'s 1 - 4**__

1. a. Seat belt, effective in all collisions. b. Over the shoulder belt, effective in all collisions. c. Turn Signals, help prevent front side and rear collisions. d. Collapsible steering wheel, effective in front, rear and turn over collisions. e. Front air bags, effective in all collisions. f. Side air bags, effective in all collisions. g. Head restrains, effective in all collisions. h. Back up sensing system, helps prevent rear collisions. i. Anti-lock braking system, helps prevent turn over collisions. j. Electronic stability control, helps prevent turn over collisions.

2.

3.

4.


 * __What do you think now?__**

I would always have my seat belt on and only drive in a car with air bags installed. If I was the driver I would make sure


 * __Inquiring Further #2__** Due Monday

**Investigate X2: Newton's FIrst Law and Seatbelts**

 * Objectives:**
 * What happens to a passenger involved in a car accident without and with a seat belt?
 * Without a seat belt they maintain their inertia when the car stops moving and continue moving forward either into the windshield or through it.
 * With a seat belt the passenger's momentum will be absorbed by the belt and they will stay in their seat unless the force of their kinetic energy is so great that they break through the belt.
 * 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.


 * 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.

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


 * **//Type of Seatbelt//** || //**Before Picture**// || //**After Picture**// || //**Description and Observations**// || //**Group**// ||
 * Thread ||  ||   ||   ||   ||
 * Wire ||  ||   ||   ||   ||
 * String ||  ||   ||   ||   ||
 * Yarn ||  ||   ||   ||   ||
 * Ribbon ||  ||   ||   ||   ||
 * 1-in masking ||  ||   ||   ||   ||

//** *Read the Physics Talk p268 - 271 before answering the following questions. * **// Questions:
 * 1) Define the terms: inertia, force and pressure.
 * 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)?
 * 4) What does Newton’s first law have to do with this?
 * 5) What materials were most effective as seatbelts? Why?
 * 6) Use Newton's first law of motion to describe the three collisions.
 * 7) 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?)

USE THE RUBRIC TO MAKE SURE YOU HAVE INCLUDED ALL REQUIREMENTS!

**Investigate X3: Energy and Air Bags**

 * Objective:**
 * How does an air bag protect you during an accident?
 * An airbag cushions your collision and causes your impact to be less severe.


 * 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.//

//(cm)// || //Cracked or smashed?// || //Description and observations// || //Length of egg in flour// //(cm)// || //Length of egg outside flour// //(cm)// || //GPE// //(j)// || //W// //(j)// || //F// //(j)// ||
 * //Egg Number// || //Drop Height//
 * 1 || 2 || Cracked || Small fractures in egg shell ||  ||   ||   ||   ||   ||
 * 1 || 4 || Cracked || Small fractures in egg shell ||  ||   ||   ||   ||   ||
 * 1 || 6 || Cracked || Small fractures in egg shell ||  ||   ||   ||   ||   ||
 * 1 || 8 || Cracked || Small fractures in egg shell ||  ||   ||   ||   ||   ||
 * 1 || 10 || Cracked || Small fractures in egg shell; peeling observed ||  ||   ||   ||   ||   ||
 * 1 || 12 || Cracked || First sign of yolk ||  ||   ||   ||   ||   ||
 * 1 || 14 || Cracked || Bottom of shell collapsed, egg-white released ||  ||   ||   ||   ||   ||
 * 1 || 16 || Cracked || Damaged continued, yolk visible ||  ||   ||   ||   ||   ||
 * 1 || 18 || Cracked || Fractures spread ||  ||   ||   ||   ||   ||
 * 1 || 20 || Cracked || Yolk is still contained ||  ||   ||   ||   ||   ||
 * 1 || 22 || Cracked || Most of egg-white released, yolk remains in shell ||  ||   ||   ||   ||   ||
 * 1 || 24 || Cracked || Yolk begins to leave shell, shell is separating ||  ||   ||   ||   ||   ||
 * 1 || 26 || Smashed || Yolk ||  ||   ||   ||   ||   ||
 * 2 || 26 || No damage || No visible damage || 2 || 3 ||  ||   ||   ||
 * 2 || 36 || No damage || No visible damage || 2.5 || 2.5 ||  ||   ||   ||
 * 2 || 46 || No damage || No visible damage || 3.5 || 1.5 ||  ||   ||   ||
 * 2 || 56 || No damage || No visible damage || 4.5 || 0.5 ||  ||   ||   ||
 * 2 || 66 || No damage || No visible damage || 4.75 || 0.25 ||  ||   ||   ||
 * 2 || 76 || No damage || No visible damage || 1.5 || 3.5 ||  ||   ||   ||
 * 2 || 86 || No damage || No visible damage || 3 || 2 ||  ||   ||   ||
 * 2 || 96 || No damage || No visible damage || 3 || 2 ||  ||   ||   ||
 * 2 || 106 || No damage || No visible damage || 3 || 2 ||  ||   ||   ||
 * 2 || 200 || No damage || No visible damage || 3 || 2 ||  ||   ||   ||


 * 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?
 * 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.

** *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) 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?

· 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. · 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?)
 * Conclusion:**

USE THE RUBRIC TO MAKE SURE YOU HAVE INCLUDED ALL REQUIREMENTS!

Section 3 Problems
4. a. 60N and 1m b. 30N and 2m c. 20N and 3m

6. a. 9,720 J b. 9,720 J c. 9,720 J/50m = 194.4 N

7. answer is b.

8. KE = 1/2mv^2 sqrt(1920 J *2/60kg) = v 8m/s = v answer is c.

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)// ||
 * .26 || .5 || .62 || 0 || .76 || .21 ||
 * 1.26 || 1.0 || .51 || 0 || 2.26 || .26 ||
 * 1.76 || 1.0 || .60 || 0 || 2.76 || .37 ||
 * 2.26 || .5 || .58 || 0 || 2.76 || .45 ||
 * 1.26 || 1.5 || .62 || 0 || 2.76 || .25 ||
 * 0.76 || 2.0 || .44 || 0 || 2.76 || .13 ||


 * 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) Find the initial momentum of the target cart for each trial.
 * 3) Find the sum of the initial momenta of the two carts for each trial.
 * 4) 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) 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.

· 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?)
 * Conclusion:**

USE THE RUBRIC TO MAKE SURE YOU HAVE INCLUDED ALL REQUIREMENTS!

**Investigate 7: Impulse and the Crumple Zone**
// Objective: A crumple zone is part of the body of a car that compresses during an impact. It absorbs the energy of the collision and lessens the force on the passengers. What are some of the factors that car designers and engineers must consider when designing a crumple zone as a safety feature? //

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

//Procedure:// // 1. On the floor, place a ramp on a stand so that one end is raised 10-cm and the other end is 20 cm from the wall. // // 2. Place a block in the cart and attach a 2-cm piece of masking tape to the front of the block and down onto the cart. Place the cart at the top of the ramp and release it. Record your observations. // // 3. Design a crumple zone to protect the block from tipping over. You can use only the following materials: one sheet of paper, 30-cm tape, 2 rubber bands, and 30-cm of string. Record your design(s) and the changes you make to it in a data table. You may want to use the available technology (still pictures and video) to supplement your written descriptions. // // 4. Measure the mass of your cart with apparatus attached. // // 5. Once you have a functional design that you are happy with, you will bring it to the front of the room to test. You will allow your cart to crash into a force sensor in order to generate a force vs. time graph, while a motion detector will measure the speed of the cart. // // 6. Click the ∑ button to get the area of the F-t Graph. Click the smart tool to get the velocity of the cart before and after the collision. // // 7. Repeat 3 times. //


 * Data and observations:** Add more columns/row as needed.
 * **Trial** || **Mass of Cart with apparatus(kg)** || **Speed of Cart** before collision(m/s) || **Speed of cart after collision (m/s)** || **Area on F-t graph (Ns)** || **Change in momentum (kgm/s)** || **Impulse (Ns)** ||
 * No Crumple Zone (teacher) ||  ||   ||   ||   ||   ||   ||
 * #1 with CZ ||  ||   ||   ||   ||   ||   ||
 * #2 with CZ ||  ||   ||   ||   ||   ||   ||
 * #3 with CZ ||  ||   ||   ||   ||   ||   ||

**Calculations:** Show equation(s), numbers plugged in, and answer with correct units. Add columns in your data table to include these results. 1. Calculate the change in momentum for your cart. 2. Impulse is equal to the area of the F-t graph. What is the impulse experienced by your cart?

***Read the Physics Talk p324 - 329 before answering the following questions.** *

1. Define the following terms: velocity, acceleration, Newton’s second law of motion, and momentum, impulse. 2. What is a crumple zone? 3. Why is it safer to collide with a soft cushion than a hard surface? 4. What is the relationship between impulse and momentum? 5. How is the impulse-momentum relationship related to Newton’s second law? 6. What were the key features of your crumple zone and why were they important?
 * Questions:**

**Conclusion:** · What are some of the factors that car designers and engineers must consider when designing a crumple zone as a safety feature? Compare and contrast crumple zones and air bags. · 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?)

USE THE RUBRIC TO MAKE SURE YOU HAVE INCLUDED ALL REQUIREMENTS!