Chapter+3

=Chapter 3: Safety =

Physics Homework & Textbook toc

What Do You See?
February 10, 2011 - car hits the wall - air bag deploys - bear gets ejected from the car - child in back seat is fine - there was music playing so the reason they crashed could be because they were distracted by the music

What Do You Think?
February 10, 2011 When you are in a car you should always wear your seat belt and sit up properly to protect yourself While you are biking I do not think it is necessary to wear a helmet if you know what you are doing and are not going fast or biking on the road I feel the same way with rollerblading, but personally I would wear a helmet, elbow pads, and knee pads

Investigate pg 260
1a. yes b. no c. no d. no e. no f. no g. no h. yes i. no j. yes k. yes l. yes m. no n. yes o. yes

3a.
 * Safety Features || Means of Protection || Pre-1960 (y/n) || New automobiles (1,2,3) ||
 * seat belts ||  || 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 in doors ||  || no || 2 ||
 * shoulder belts for all seats ||  || no || 1 ||
 * anti-lock braking systems ||  || no || 1 ||
 * tempered shatterproof 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 pg. 263
- Safety was not always a major consideration in automotive manufacturing. - Turning point in history of automobile safety occurred when Ralph Nader, an American attorney and political activist, wrote the book Unsafe at Any Speed in 1965. This book highlighted the problems of not having seat belts in vehicles.

Checking Up pg. 263
1. Since 1960, manufacturers have made vehicles safer with seat belts, anti- lock breaks, and 4WD 2. There are two explanations for the increase in fatal 4WD crashes. The first is the growing number of kilometers traveled by 4WDs or it could also be because of the tendency of some drivers to increase speed under the impression that the safety features will protect them.

What Do you Think Now? pg. 264
In order to prevent serious injury when an accident occurs. I would make sure my seat belt is put on properly, make sure my face is covered in case of shattering glass, make sure my legs are placed properly in the car and not on an arm rest.

Physics To Go pg. 265
2. Helmet, sneakers, proper biking apparel, elbow pads, knee pads, tire pressure is checked, and make sure breaks work 3. Helmet, knee pads, elbow pads, and make sure wheels are secure and rolling properly 4. 2. Safety features for bikes can be helmet, knee pads, and reflectors. 3. Safety features for in-line skating can be helmet, knee pads, elbow pads, and even a mouth piece. 4. For skateboarding you can use a helmet, elbow pads, and even a mouth piece. 5. Seat belt, sit up properly, do not drive recklessly

What Do You See?pg. 266
February 15, 2011 two cars in test accident one person listened to the sign, and he was safe other person did not listen, and got thrown from the car projectile motion (moving in a parabola) no dog :(

What Do You Think?pg. 266
February 15, 2011 The way it is designed would be different In a regular car you are strapped in across the waist and one shoulder Since a racecar driver is going a lot faster I feel he should be strapped in more I think the seat belt should look like an "X" where one strap crosses over the left should and the other should comes across the right shoulder. This way he will be able to feel more secure and be protected if he gets into an accident

Investigate pg. 267
Part A: 2a. falls out 3a. falls out at a faster speed and falls farther away from the car Part B: 2a. 36 cm 3a. Thin Ribbon: A lot better than the wire, but he still fell out Thick Ribbon: Did not move 3b. His head is the most vulnerable, because it jolts with the impact 4a. The crash dummy driver slams their head into the windshield or falls out of the car. 4b. The dummy's head and arms have the most risk of getting hurt because in the movie we saw their heads hitting into the windshield, and sometimes their arms fell off.

Physics Talk pg. 268
There are three distinct parts of Newton's First Law of Motion - Part 1: object stays at rest - Part 2: object in motion stays at motion in a straight line with constant speed - Part 3: says part 1 and 2 are only true when the net force, or total of all forces, on the object is zero. An object may have forces acting on it and still have no change in its motion
 * Newton's First Law of Motion:** an object at rest will stay at rest, and an object in a straight line with constant speed unless acted upon by a net, external force


 * Inertia:** The natural tendency of an object to remain at rest or to remain moving with constant speed in a straight line
 * 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 (newtons per meter squared) or Pa (pascals)

Physics Plus pg. 271
1a. 10 N/m^2 1b. 50 N/m^2 1c. .66N/m^2 1d. 2.5 N/m^2 2a. 35,000 N/m^2

Physics To Go pg. 274
1a. 1b. The car moves forward and then you move forward with the car. According to Newton's first law 1c. The object remain will remain in motion, even when the brakes are applied 2. 3. Going to fly over the curb and hurt himself, the skateboard stops because an opposite force acted upon it 4. first collision- The automobile strikes the pole and then the pole exerts a force that brings the automobile to rest. second collision- When the automobile stops, the body keeps moving. third collision- the body stops but the heart, the brain, and other organs keep moving 5. The wire has less surface area so it would cut through you 6. Yes, it saves your life. You should not have a legal right to say no, because some people do not realize how much a seat belt can help you in a positive way. 7a. He/she would say it's uncomfortable and it's my choice 7b. It's a safety precaution and you should wear it, and since I am the driver I say you need to wear a seat belt and if you have a problem with that, find another ride 8. The brain wants to stay where it is, but the skull moves over and crashes into the brain 9.

What Do You See? pg. 277
- Two cars run into each other - One person is wearing a seat belt, the other person is not - The person wearing the seat belt air bag's deployed - One bystander looking at the person with no seatbelt or airbags looks upset - Other bystander has a happy face looking at the person with a seat belt and an airbag - Both cars are damaged (3rd law of motion)

What Do You Think? pg. 277
It catches your head and embraces your head instead of just stopping it. This slows your head down gradually, which makes it less likely for you to get hurt.

Investigate pg. 277-278
2. Little tiny crack 3. 2cm 4. 22cm 5. Rice spills out of the petri dish, but the egg does not crack 6. .5cm 7. The rice provided a cushion for the egg, which made this egg not crack. This is compared to the egg we previously dropped that had no cushion and did crack 8.

NOTES What is the force exerted on the egg IF it drops 95 cm onto a bowl of rice - compressing the rice .50 cm m=55g We need to reduce the speed of the egg to 0 m/s -We had to get rid of the KE - It takes work to change the KE of an object W=∆KE Fd=KE(final) - KE(initial) Fd= 0 - 1/2mvi^2 w=deltaKE F= -mvi^2/2d ❍ ⇐ (egg) v=0 V Vi Rice

1st determine the velocity of the egg it arrives at the surface of the rice

vi= 0 vf = ? a = -9.8m/s^2 d = .95m t = ?

vf^2= vi^2 + 2ad vf^2= 0 + 2(-9.8)(-.95) vf= 4.3 m/s

F=-mvi^2/2d F=-(.055)(4.3)^2/2(.05) F= -10N

m=55g=.055kg d=5cm=.05m

Physics Talk pg 279
- Kinetic energy: the energy possessed by a moving body is called kinetic energy KE=1/2mv^2 - Work: amount of force applied on an object over a certain distance W=FxD In order to stop an automobile safely the brakes must slow the speed of the vehicle getting rid of the KE

Checking Up pg 287
1. The mass of the vehicle and the velocity the vehicle is traveling at 2. When work is done, the kinetic energy can either increase or decrease depending on direction of force 3. You need to apply an equal force to stop it. 4.KE and work are both measured in joules

Physics To Go pg. 290
1a. When you throw a ball a force is applied. When the ball is moving through the air the ball uses kinetic energy. When the ball hits the glove it negatively accelerates and energy is lost which is why the ball stops. 1b. Jumping creates GPE because your body is being pulled down. You then negatively accelerate and the energy is lost and you stop. You bend your knees as you come down because if you jump with straight legs the impact will break your knees. By bending you cushion your fall. 1c. During a bungee jump GPE and EPE are both present. The EPE sends you up, and the GPE pulls you back down to the ground. 1d. A wrestling mat acts as a cushion when the person falls. It makes the person fall slower then he would have if there was no mat. 2. ke=mv^2 9x 3.ke=mv^2 4x 4. w=fd 5. 6a. KE=1/2mv^2 KE=1/2 (60) 18^2 KE=9720J 6b. w=fd w=9720j 6c.ke/d= 194 7. B 8. C
 * Force || Distance ||
 * 60N || 1m ||
 * 30N || 2m ||
 * 20N || 3m ||
 * 12N || 5m ||
 * 10N || 6m ||
 * 6N || 10m ||
 * 3N || 20m ||
 * KE || M || SPEED ||
 * 500j || 1000kg || 1m/s ||
 * 200,000j || 1000kg || 20m/s ||
 * 100,000j || 500kg || 20m/s ||
 * 50,000j || 500kg || 10m/s ||
 * 450,000 || 1000kg || 30m/s ||

What Do You Think Now? pg. 291
Airbags can cause injury in people that do not follow the rules of sitting in the passengers seat. If you are under the required weight/age that you are supposed to be in order to sit in a passengers seat in can cause serious injury. Also, if you are not sitting up properly, and the airbags deploy you can cause injury to your body.

What Do You See? pg. 292
In the cartoon the person in the small red car gets rear ended by the big truck. In the collision the person in the red car gets whiplash.

What Do You Think? pg. 292
Whiplash is when your neck gets whipped back and forth. It is the result of having your head get flung back and forth It is more prominent in a rear-end collision, because your body is moving foward and your head is not, therefore your head is left behind. It does not happen in a front end collision, because your whole body is moving and then you collide with the airbag and the force of the airbag slows you down. There is nothing to slow you down in a rear end collision, which is why whiplash happens more often during a rear-end collision

Investigate pg. 293
7a. Car A had a head rest in it. When car B hit car A from the rear, the head rest prevents the head from having whiplash. Car C had no car rest. When car B hit car C from behind the person suffered whiplash and in a real accident his neck probably would have snapped.

Physics Talk pg. 294
Newton's Second Law of Motion: 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 Newton's second law of motion allows you to make predictions about what happens when an unbalanced external force is applied to an object. It indicates that the change in motion is determined by the net force acting on the object Whiplash: The common name for a type of neck injury to muscles of the neck f=ma a=f/m

Checking Up pg. 297
1. Head rests and airbags help prevent a whiplash injury. 2. Whip lash occurs more often when a car gets hit in the rear. During the collision your body moves forward without your head. Then your head snaps forward and backwards right after. 3. Your body is accelerates forward by the force of the seat, but your head wants to stay in place. If there is no headrest, your head will accelerate forward by your very, over stretched, bent neck. To you, it feels as if your head is snapped backwards, but what’s really happening is your body is being accelerated forward and your head is being left behind.

Physics To Go pg.299
1. Your body is moving forward while your head is still at rest, this only happens during a rear end collision. 2. The boxes in the truck are still moving forward, because a force has not acted upon the box to stop it. 3. The people on the bus want to remain at rest and it takes them a while to accelerate with the bus 4. There is no head rest 5. Rear end 6. Better seats, with headrests and crumble zone in a car 7. Headrests prevent you head from going all the way back, which would cause your neck to get torn and stretched out. 8. D,A,C,E,C,B

What Do You See? pg. 304
Small car is hitting bigger car The small car cannot apply enough force to move the big car

What Do You Think? pg. 304
THINGS THAT MATTER: design of car where the car gets hit size of car crumple zone

It depends how hard the small car hits the big car, the small car will have the most damage

Investigate pg. 304
2a. The car that hit the car at rest stops. The car at rest moves forward 3a. Same results, but the car at rest moves at a faster rate traveling further 3b. The car at rest moves faster 3c. A car is stopped a red light and gets hit from behind 5a. The car with the weights on it keeps moving instead of staying at rest. The car at rest keeps moving too 5b. If a big truck hits a little car, that is waiting for the red light 5c. The car at rest moves, the car that hit it moves but in the opposite direction (springing back) 6a. When the cars hit, the car at rest continues forward, the other car springs back 6b. small car hits big truck 6c. moves faster 7a. The 7b.

Physics Talk pg. 306
Momentum: the product of the mass and the velocity of an object; momentum is vector quantity p=mass x velocity

Checking up pg. 307
1. The eagle has more momentum, because it has a higer mass 2. Transfer momentum has to do with mass and velocity 3. The skateboarder would go flying, because the car has such a greater momentum

Physics To Go pg. 309
1. The car at rest moves because the momentum is transferred. The car that hits the car at rest goes from having all the momentum to none of the momentum because it comes to a halt when it hits the other car. 2. The bounce off one another, and the velocity changes direction 3. The bigger car has a greater momentum, so it propels the other car forward. 4. Because of their size, it is tougher to move and to push them backwards so it's better to have them on their team. During a collision the player with the greater momentum will make the other person bounce back. 5. The mass and velocity of the vehicles directly affect the collision and the result from it. 6. It would only have to travel 1m/s because because it's mass times velocity.

What Do You See? pg. 310
Car 1 is moving at a fast speed down a ramp. It then hits into car 2. Measuring the distance or the time Persons head in car one is staying in place but it looks like it's going backward

What Do You Think? pg. 310
1. Tires streaks 2. the damage on the cars 3. momentum 4. time 5. distance 6. mass

Investigate pg. 311
1a. before Collision || Velocity of Object 2 before collision || Mass of Combined objects after collision || Velocity of Combined objects after collision ||
 * Mass of Object 1 || Mass of Object 2 || Velocity of Object 1
 * 250 kg || 250kg || .71 m/s || 0 m/s || 500 kg || .32 m/s ||
 * 500 kg || 250kg || .6 m/s || 0 m/s || 750 kg || .34 m/s ||
 * 750 kg || 250 kg || .45 m/s || 0 m/s || 1000 kg || .28 m/s ||

3a.

Momentum of Object before and after Collisions Momentum = Mass x Velocity Momentum of Object 1 || Before the Collision Momentum of Object 2 || After the Collision Momentum of Combined 1 & 2 ||
 * Before the Collision
 * 177.5 || 0 || 160 ||
 * 300 || 0 || 255 ||
 * 337.5 || 0 || 280 ||

3c. before: 815 after: 695 3d. The momentum decreases 4a.

Physics Talk pg. 312
momentum BEFORE collision= momentum AFTER collision m1v1 + m2v2= (m1+m2)vf
 * 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

Checking Up pg. 315
1. The law of conservation of momentum is that the momentum before a collision is equal to the momentum after the collisosn 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 pg. 319
1. 3. 3 m/s 4. By having an external force acting upon it 5. Vehicle B gains 4,000 kg m/s so the total is 8,000 kg m/s 6. 2 + 3 = 5 m/s 7. 10 + 9.78 = 7.78 m/s

8. M1V1i+M2V2i=(M1+M2)VF 3(2) + 1(2) = (3+1)vf 6+2=4vf vf=4 m/s

9. m1v1 + m2v2= (m1+m2)vi 45(2)+75v2=0 90+75v2=0 75v2=-90 v2=-1.2 m/s

10. MaVai+MbVbi=MaVaF+MbVb .35(20) +.06(-30)= .35(10)+.06(x) 7-1.8=3.5+.06x 5.2-3.5=.6x 1.7=.6x 28 m/s

11. MaVai+MbVbi=MaVaF+MbVbF 3(0)+1(4)=3(2)+1f 4=6+f f=-2 m/s

12. M1V1i+M2V2i=(M1+M2)VF 90(0)+.16(30)=(90+.16)VF 4.8=90.16VF .05 m/s

13. M1V1i+M2V2i=(M1+M2)VF 45(1.1)+.08(0)=(45+.08)VF 49.5=45.08VF 1.1 m/s

14.M1V1i+M2V2i=M1V1F+M2V2F 1700(10)+M2(-25)=1700(-5)+M2(3.75) 17000+-25M2=-8500+3.75M2 25500=21.25M2 1200 kg

15.M1:1.67x10^27kg V1:2.50x10^5 M2:? V2:0 V1f:-1.10x10^5 6x10^ -22

16. coeff fric:.15 m1: .04kg v1: 200 m2: 20kg v2:0 vf: ?

.4

M1V1i+M2V2i=(M1+M2)VF
 * use when they are stuck together with the same speed

M1V1i+M2V2i=M1V1F+M2V2F=
 * for something that hits and bounces off

What Do You See? pg. 321
Guy is going at a fast speed down a ramp His "legs" are going to cushion him when he runs into the wall (crumple zone) There is a man taking down calculations The guy in the car's hat falls off, which shows he is accelerating There is a dog

What Do You Think? pg. 321
crumple zone has to be longer so you don't get hurt where the hood is and where there feet will be placed

Physics Talk pg. 324
W=fd=∆KE Velocity: speed in a given direction; displacement divided by the time interval; velocity is a vector quantity; it has magnitude and direction Acceleration: the change in velocity per unit time; acceleration is a vector quantity Newton's Second Law of Motion: if a body is acted upon by a net external force, it will accelerate in the direction of the net force with an acceleration proportional to the force and inversely proportional to the mass Momentum: the product of the mass and velocity of an object; momentum is a vector quantity Impulse: a change in momentum of an object

Checking Up pg. 329
1. A crumple zone is something you put in a car to slow down the force of the car during a crash 2. It is safer to collide with a soft cushion because it reduces force, while a hard cushion causes the car to bounce back 3. Momentum is the product of the mass and the velocity of object 4. Impulse is a change in momentum of an object

Physics To Go pg. 2
1. Impulse and Newton's first law both have to deal with force. This affects the crumple zone because you need a lower force which has a smaller impact 2. The crumple zone increases the time of the collision which reduces the force making it slow down gradually, and the airbag protect the people in the car from whiplash 3a. by increasing the time you are going to reduce acceleration 3b. the person will slow down more gradually because there is more time for the force 4. You bend your knees because they absorb some of the force as you hit the ground 5. They would use a lot of padding so it uses less force over more time 6a. ∆ p=m∆v = 1200kg (0-10) =-12,000 N 6b. ∆ p=m∆v = 1200(5-10) = 6,000 N 7. ft=m∆v ∆v=ft/m -10,1000(1,25)/1200 =-10m/s

8. 75,000N 9. There is less force over more time 10. The graph on the left is the result of a hard cushion. The hard cushion has a larger force acting over a shorter period of time. For the safety of passengers, it is better to have a small force over a longer period of time (graph on the right) impluse is the same for both graphs

Practice Test pg. 340
1. b 2. d 3. a 4. b 5. D 6. A 7. A 8. C 9.C (5)(7)=35 (.4)(30)=12 (20)(2)=40 (.3)(60)=18 10. D 11. A 12. B 13. D (2)(3)+(6)(1)=12 14. B 15. C 16a. determine the mass and velocity 16b. calculate momentum and compare 16c. no additional measurements needed to look at the intial and final KE 17a. First law 17b. first and second law 17c. first and second law 18. Increases time of momentum decreasing the force 19a. The wider belt because force is spread out 19b. If it stretched the passenger can gradually slow down 20a. GPE=mgh trial 1: GPE=(2)(9.8)(.3) GPE= 5.8 trial 2: GPE=(1)(9.8)(.5) GPE=4.9 20b. KE=1/2mv^2 trial 1: KW=(1/2)(2) 20c. W=fd trial 1 21. 1500(20)= 30000 30000/10=3000 3000/1500=20mph 22. MaVai+MbVbi=(Ma+Mb)Vf (120)(5)+(80)(10)=(120+80)Vf Vf=7m/s 23. (.160)(40)=6.4 (.160)(60)=9.6 =3.2m