Chapter+3

= = toc =Section 1: Safety Features=

**What Do You See?**
**2/14/2011** The car was launched, the front of the car is all smashed. The baby, however, is completely safe.

What Do You Think?
2/14/2011 Wear a helmet on skates and a bicycle. Wear a seatbelt in the car.

Investigate
2/14/2011 1a. false 1b. false 1c. false 1d. false 1e. false 1f. false 1g. false 1h. true 1i. false 1j. true 1k. true 1l. true 1m. false 1n. true 1o. true

3.
 * Safety Features || Means of Protection || Pre-1960 automobiles (y/n) || New Automobiles (1,2,3) ||
 * Seatbelts ||  || yes || 1 ||
 * Head restraints ||  || yes || 1 ||
 * Front Airbags ||  || no || 1 ||
 * Back-Up Sensing System ||  || no || 2 ||
 * Front crumple Zones ||  || no || 1 ||
 * Rear Crumple Zones ||  || no || 1 ||
 * Side-impact beams on Doors ||  || no || 2 ||
 * Shoulder belt For All Seats ||  || no || 1 ||
 * Anti-Lock Braking Systems (ABS) ||  || no || 1 ||
 * Tempered Shatter-proof Glass ||  || no || 1 ||
 * Side Airbags ||  || no || 2 ||
 * Turn Signals ||  || yes || 1 ||
 * Electronic Stability Control ||  || no || 2 ||
 * Energy-absorbing Collapsible Steering Column ||  || no || 1 ||

Physics Talk
2/14/2011 Engineers build automobiles in order to make civilians safer in case of accidents. Increase of fatal 4WD crashes could be due to either the growing rate of KM traveled by 4WDs and the tendency of drivers to speed.

Checking Up
2/14/2011 1. Seat belts, Hard chrome dashboards, and solid steering columns 2. The increasing rate of KM and the speeding of drivers

Physics To Go
2/14/2011 2. Brakes 3. Braking pad 4. Brakes again. 5. Seat belts, airbags, shatterproof glass, turn signal, brakes

=Section 2=

What Do You See?
2/15/2011 2 smiling crash dummies hitting the wall and one is flying in the air

What Do You Think?
2/15/2011 The safety features would have to be quite superior. A faster traveling car requires more safety features because one collision will exert way more force than a normal, 60mph car crash. This means that the seat belt should be able to secure more weight and force than a normal seat belt. A thick strap would distribute the force more efficiently compared to a thin strap.

Investigate
2/15/2011

Part A:
2a. The passenger flies off the car and hits the textbook 3a. The passenger flies at a greater velocity into the wall. It's similar because both the passengers at both speeds always flew off.

Part B:
2a. Significant injury occurs at 45 cm 3a Half a CM Ribbon: The passenger received slight injury during the half CM seatbelt ribbon test. A quarter of a CM Ribbon: There was a greater injury compared to the .5 CM 3b. The difference in injury is from the width of the material used, and the speed. The higher the speed, and the smaller the width, the greater the injury. The lower the speed, and the bigger the width, the lesser the injury.

Physics Talk
Newton's First Law - An object at rest stays at rest Inertia - the tendency of an object to remain at rest or remain moving 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 (P=F/A)

Checking Up
1. An object in motion will stay in motion 2. Newton's first law 3. First collision - automobile strikes pole and pole exterts force that brings automobile to rest Second collision - when the automobile stops, body keeps moving Third collision - the body stops but the heart, the brain, and other organs keep moving 4. Inertia is the tendency of an object to remain at rest or remain moving 5. The force was spread out in a bigger area so the pressure is less

Active Physics Plus
1a. 10 N/m^2 1b. 50 N/m^2 1c. .66 N/m^2 1d. 250 N/m^2 2a. 17,500 N/m^2 2b. 35,000 N/m^2, pressure is twice as much because the area is half as much

Physics to Go
1b. The car is at rest until the accelerator is pushed. 1c. The object in the back of the car is still in motion while the car is stopping 1d. The seat belt prevents the person from continuing to move with the car, basically applying an unbalanced force to the unbalanced force. 2. A snowplow is in motion on the road, pushing the snow that was at rest to the front and the sides. A person on a bike presses the breaks and stops moving. 3. The skater's skateboard would stop but he would continue going and flip over the curb. 4. First collision - automobile strikes pole and pole exterts force that brings automobile to rest Second collision - when the automobile stops, body keeps moving Third collision - the body stops but the heart, the brain, and other organs keep moving 5. Since there is less of an area, there would be more pressure on the body 6. Yes because seat belts can save people's lives 7a. They would be safer in an accident if they were wearing a seatbelt 7b. If the car crashes, you would remain in motion and fly forward 8. The body is stopped, but the picture shows the brain keeps moving 9. .8m

= Section 3 =

What Do You See?
One guy has an airbag and the other one doesn't and hits his head

What Do You Think?
It slows you down gradually

Investigate
3a. Crack height: 6cm 4a. Smash height: 20cm 5a. It doesn't seem to crack until the egg's inertia knocks all the rise out of the dish. Even after dropping it from a meter it still didn't break. 6a. The indentation increased with every 5cm by 1 mm. 7a. While egg #1 broke, egg #2 didn't even have a slightest fracture. 8a. The sheet is flexible to let the egg receive a gradually descending acceleration.

Physics To Go
3/1/2011 1a. The stopping distance is greater because the catcher moves his mitt backwards, reducing force 1b. Stopping distance is greater because the knees are bent, reducing force and converting energy more efficiently 1c. the cord is stretched out which lets off energy 1d. it takes pressure away when the wrestler hits the mat 2. 9 3. the egg thrown faster will travel twice as far 4. 30 feet and 2 N, 10 feet 6 N, 60 feet, 1 N 5. 6a. 9720J 6b. 9720J 6c. 194J 7. B 8. 8m/s C

=Section 4=

What Do You See?
3/3/2011 The dummie is getting hit from the back by a car, and his head is thrown back and forth violently.

What Do You Think?
3/3/2011 Whiplash is when your head goes back extremely fast, then snaps forward. Rear end collisions have more whiplash because just the head stays still while the body moves forward.

Investigate
3/3/2011 7a. The dummie's head is completely messed up 7b. The object is at rest, until suddenly acted upon by another force(the other car), so the head stays still but the body moves forward.

Physics Talk
3/3/2011 Newton's Second Law - if a body is acted on by an unbalanced force, it will accelerate in the direction of the unbalanced force. The acceleration will be larger for smaller masses. The acceleration can be an increase in speed, a decrease in speed, or a change in direction Whiplash - the common name for type of neck injury to muscles of the neck

Checking Up
3/3/2011 1. Headrest and crumple zone 2. The body moving forward and the head remaining still causes the head to snap backward. The neck muscles and bones of the vertebral column become damaged 3. First law- a car stopped at a red light the driver is at rest within the car. Second law- automobile begins to move and backseat pushes driver forwards

Physics To Go
3/3/2011 1. The car is moving and the head is flung back 2. Newton's first law- the package stays in motion 3. The passengers stay in place but the bus moves forward so it feels like they are moving forwards 4. There is no headrest 5. Rear-end collision because the head whips back and forth 6. Headrests 7. The head rest keeps the head in place

=Section 5=

What Do You See?
3/7/2011 There is a dummie in a go kart crashing into a monster truck.

What Do You Think?
3/7/2011 The factor that determine the severity of the crash come from the speed and the mass of each object. The driver of the sports car will probably sustain more injury because there is more force being exerted into the sports car than the monster truck.

Investigate
3/7/2011 2a. The moving car basically stops, while pushing the standing car in the direction of its acceleration 3a. The moving car stops more drastically, while exerting its energy into the standing car making the standing car move even faster 3b. The results are more drastic, the moving car stops faster and the standing car moves faster 3c. A moving car hitting a parked car. 4. Both cars accelerate slower than before. The moving car accelerates negatively slower than it did before, and the still car accelerates positively slower than it did before. 5a. The larger car still accelerates negatively slower than it would if it had less mass, but the less mass car accelerates even faster than it did with more weight. 5b. A truck hitting a parked sedan 5c. The small mass car bounces backwards, off the larger mass car 6a. The small mass car basically bounces off the larger mass car, barely moving the larger mass car 6b. A sedan crashing into a parked truck 6c. Yes, the same as the results in 5a. 7a. Cart A had the greater mass because when the other car crashed onto it, the other car bounced back 7b. Yes, I was correct. The way the cars move during a collision can determine the weight of each car, or which car weighs more.

Physics Talk
3/7/2011 Momentum - The product of the mass and the velocity of an object; momentum is a vector quantity (p=mv)

Checking Up
3/7/2011 1. Eagle 2. Momentum is transferred when one objects collides with another object 3. If a car hit a skateboarder, the skateboarder would sustain way more damage since the mass of the car is more than that of a person.

Physics To Go
3/8/2011 1. The moving vehicle will push the parked vehicle 2. Both cars will bounce off eachother 3. The heavier car will push back the lighter car while remaining still after the impact 4. Football teams require heavy linemen in order to both cause maximum damage, and play solid defense. 5. The mass and speed of the vehicles 6. 1m/s.

=Section 6=

What Do You See?
3/8/2011 Two people timing the roller coaster with the dummie heading from an incline downwards. The car is accelerating negatively and his head is snapping backwards.

What Do You Think?
3/8/2011 Traffic-accident investigators probably use momentum, friction, the safety features of the car, etc.

Investigate
3/8/2011 1. 2. (Last few rows of the table)
 * Mass of object 1(kg) || Mass of object 2(kg) || Velocity of object 1 before collision (m/s) || Velocity of object 2 before collision || Mass of combined objects after || Velocity of combined objects after collision ||
 * 250 || 250 || 0.6m/s || 0 || 500 || 0.4m/s ||
 * 500 || 250 || 0.8m/s || 0 || 750 || 0.6m/s ||
 * 250 || 500 || 0.8m/s || 0 || 750 || 0.4m/s ||
 * 500 || 500 || 0.55m/s || 0 || 1000 || 0.35m/s ||
 * 750 || 250 || 0.8m/s || 0 || 1000 || 0.7m/s ||

3. 3d. The momentum is always greater after the collision than before, in a sticky collision.
 * Momentum of Object 1 Before || Momentum of Object 2 Before || Momentum of objects After ||
 * 150 || 0 || 200 ||
 * 400 || 0 || 450 ||
 * 200 || 0 || 300 ||
 * 275 || 0 || 350 ||
 * 600 || 0 || 700 ||

4a.

Physics Talk
3/10/2011 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 momentum BEFORE collision= momentum AFTER collision (m1v1 + m2v2= (m1+m2)vf)

Checking Up
3/10/2011 1. The momentum before a collision is equal to the momentum after the collision 2. If you add up all of the momenta before a collision you know the sum of all the momenta after the collision will be the same because total momentum is conserved 3. 6,000 kgm/s

Physics To Go
3/10/2011 2a. p=mv p = 2kgm/s 2b. 4kgm/s 2c. 4 kgm/s

3. m1v1 + m2v2= (m1+m2)vf mv1 + mv2 = 2mvf ms cancel out v1 + v2 = 2vf vf = 4 v1+v2 = 8m/s 4. external force acting

5. Vehicle B gains 4000, so the total is 0

6. m1v1 + m2v2= (m1+m2)vf mv1 + mv2 = 2mvf v1 + v2 = 2vf 3 + 2 = 5 2vf = 5 vf = 2.5 m/s

7. m1v1 + m2v2= m1vf1 +m2vf2 80(10) + (100)(8) = 1600 1600 = 100(9.78) + 80(vf2) vf2 = 7.775

8. m1v1=m2v2 3(2)+1(2)=(3+1)vf vf=4

9. m1v1 + m2v2= m1vf1 +m2vf2 0 = (45)*2 + (75) *vf2 vf2 = -1.2m/s

10. 28m/s 11. -2 m/s 12. .05 m/s 13. 1.1 m/s 14. 1200 kg

=Section 7=

What Do You See?
3/15/2011 There is a dummy in a cart with a spring in the front crashing into a barrier. There is another dummy marking the results.

What Do You Think?
3/15/2011 How much force the crumple zone absorbs, and the amount of time it takes to absorb it.

Physics Talk
3/23/2011

Checking Up
3/23/2011 1. A crumple zone reduces the force that impacts the passenger(s) 2. Impulse is force over time. The longer the time, the lesser the force. Softer surfaces have longer times than harder surfaces, therefore the forces are less. 3. The mass of something times its velocity 4. Impulse is force times time and momentum is velocity times mass.

Physics To Go
3/23/2011 1. Impulse and Newton's first law play a role in designing a crumple zone because force needs to be exerted over a longer time, and inertia has to be reduced. 2. The crumple zone reduces the force the actual passenger takes, then the airbag pops up for additional force reduction over a longer period of time. 3a. Newton's Second Law - The negative acceleration taken is less with a cushioned surface because the time the force takes to completely exert is longer. 3b. Impulse/Momentum - Cushioned surfaces provide longer times, thereby effectively decreasing the force exerted 4. Bending knees increases the time it takes for the force to fully exert, therefore decreasing the overall force 5. The designers can provide some type of cushion to increase time 6a. 24,000 6b. 18,000 7. Impulse - 12,000 Change in momentum after 1.2 s - 14,400 8. 75,000N 9. 2,678 N is exerted if the time is increased to 2.8 seconds. 2,678 N is significantly less than 75,000N 10. First graph has a high amount of force exerted over a certain period of time, and the second graph has a lower amount of force exerted over a slightly longer period of time.

=Crumple Zone Project=

Video of Two Different Carts
media type="file" key="crumple zone.mov" width="300" height="300"

=Practice Test=