Chapter+3

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= Section 1 = toc

What Do You See Now?
Page 260, February 9th, 2011 I see a test car with test dummies inside of it crashing into a wall. The front of the car is crushed and the airbag on the drivers side has gone off. The momentum has caused the occupants to move forward and the back of the car is off the ground from the force of impact. There is a music note which indicates noise, from the crumpling of the car and the noise of the impact itself. This means that energy is being consumed.

What Do You Think?
Page 260, February 9th, 2011 Defensive Driving, use all proper safety mechanisms, wear a helmet, take courses (drivers ed).

Investigate
Page 260, February 9th, 2011 1a. T x 1b. F x 1c. F x 1d. F 1e. F 1f. F x 1g. F 1h. T 1i. F x 1j. T 1k. F 1l. F 1m. F 1n. T 1o. T 10/15 2a. 3.
 * Safety Features || Means of Protection || Pre-1960 || Modern ||
 * seat belts || keep you from ejecting || X ||  ||
 * head restraints || protect your head || X ||  ||
 * front airbags || protect your body from injury ||  || X ||
 * back-up sensing system || make sure you don't hit anyone ||  || X ||
 * front crumple zone || make sure the front section doesn't crumple on you ||  || X ||
 * rear crumple zones || make sure the back section doesn't crumple on you ||  || X ||
 * side-impact beams || make sure the side doesn't crumple || X ||  ||
 * shoulder belts || make sure you don't fly out ||  || X ||
 * anti-lock brakes || so you don't skid when breaking hard ||  || X ||
 * tempered glass || so you don't get cut ||  || X ||
 * side airbags || so you don't hit the side of the car ||  || X ||
 * turn signals || so people know you're turning || X ||  ||
 * electronic stability control || to prevent accidents ||  || X ||
 * energy-absorbing collapsible steering || to keep you safe ||  || X ||

Physics Talk
Page 263, February 10th, 2011 Before 1965, safety was not a main concern in the automotive industry. Since then, safety has improved greatly in cars, and they have been made much safer. 1. Vehicle manufacturers have made their vehicles safer by including safety belts, making collapsable drive columns, and removing solid chrome dashboards. 2. That those who have 4WD vehicles travel greater distances, and those with 4WD vehicles drive faster thinking they are safer.

Physics To Go
Page 265, February 10th, 2011 1. Front Airbags - F Back-up sensing system- R Front crumple zone - F Rear crumple zone - R Collapsible Steering - F Tempered Glass - F Anti-Lock Brakes - F Shoulder Belts - F Side Airbags - S 2. Helmets, shoulder and knee pads, better tires, brakes. 3. Helmets, shoulder and knee pads, better skates. 4. Helmets, shoulder and knee pads, more stable skateboards. 5. Those that are included in the chart above. 6. My parents have all of the things included in the chart above, they think they have very safe vehicles by today's standards.

=Section 2=

What Do You See?
Page 266, February 15th, 2011 The picture shows two cars, the first car crashed into a wall and the driver was wearing a seat belt. The second car crashed into the back of the first car, and the driver was not wearing a seatbelt so he was ejected out of the car and is traveling with parabolic motion. The first car is crumpled at the crumple zones in the front and back of the car.

What Do You Think?
Page 266, February 15th, 2011 I think that the seat belt designed for high speed crashes should be different than a regular seat belt. The seat belt in a high speed crash should be similar to a harness, which distributes the force of negative acceleration throughout your entire body. A harness design would also be more stable and effective than the traditional seat belt at high speeds.

Investigate
2a. The passenger flew off the cart and landed on the textbook, with several arm injuries. 3a. The passenger flew off and was decapitated, he also sustained arm and leg injuries. Part B 2a. The ramp is a height of 50cm. 3a. The thin copper wire led to long cuts across the abdomen The thin ribbon resulted in deformation of his abdomen, some "bruising". The thick ribbon resulted in significantly less bruising and damage. 3b. The larger the surface area, the less force exerted on a given area on the dummy is less, and therefore there is less damage. 4a. The crash-test dummy flies in the direction the vehicle was moving. 4b. The head and abdominal area seem to be in greatest danger in a crash. ==

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Active Physics Plus
Page 272, February 15th, 2011 1a. 10N/1m^2= 10N/m2 1b. 10N/0.2m^2= 50N/m2 1c. 10N/15m^2= .66N/m2 1d. 10N/4m^2= 250N/m2 2a. 700N/.04m^2= 17500N/m2 2b. 700N/.02m^2= 35000N/m2

Physics Talk
Newtons first law, an object at rest will stay at rest and an object in motion will stay in motion. In crashes, cars exert forces on different objects, such as different cars and walls. Pressure is the force in a given area, and is found from the equation P=f/a, where f is the force and a is the area.

Checking Up
Page 271, February 15th, 2011 1. Because of Newton's First Law, an object at rest stays at rest and an object in motion stays in motion. 2. Because the driver is moving as fast as the car, and when the car stops inertia causes them to continue moving. 3. One collision occurs, and the force of the car crashes into another. Another occurs, and the force is transferred from the first crashed car into the second, and so on. 4. Inertia is the tendency to do nothing or remain constant. 5. The force is spread out over a larger area, and the pressure therefore is lower.

Physics To Go
Page 274, February 15th, 2011 1a. Your brakes apply a force to the tires, which helps slow the car down. 1b. The accelerator causes the engine to move faster, which applies a force to the tires to cause the car to start moving. 1c. The object in the back of the vehicle is moving at the same speed as the car, and when the brakes are applied there is no force to stop the object in the car from continuing at the same speed. 1d. The car suddenly stops, and instead of continuing at the same speed, the seat belt helps to slow the person down to the same speed as the car. 2. Brakes in a bicycle help it to stop, and peddling helps them accelerate. 3. When the skateboard hits the curb, the person will continue to travel past the curb, as inertia means they will remain at the same speed as they were. 4. In the first collision the car comes to rest, in the second the inside of the vehicle helps to slow down the person, and in the third the organs will slow down when they impact the rest of the body. 5. The pressure exerted by a wire is more than a regular seat belt, which would cause damage to the person using it. 6. Yes, I think that they are fair because they help keep people safe and reduce death and injury. 7a. It is stupid or childish to wear, or it might be uncomfortable or irritating. 7b. Seat belts keep you safe, and you may face permanent damage or death. 8. The punch causes the head to move backward, but the brain stays where it originally was, causing it to hit the side of the skull.

=Section 3=

What Do You See?
Page 277, February 16th, 2011 I see two cars, one with the air bags deployed, and one with no air bags. The person in the car with no air bags deployed is hitting the windshield. With stars above the person indicating pain.

What Do You Think?
Page 277, February 16th, 2011 An air bag protects you during an accident because it slows down your body and makes sure you don't slam into the windshield or be ejected from the car.

Investigate
Page 277, February 17th 2011 3a. The crack height was equal to 6 cm. 4a. The smash height was equal to 12 cm. 5a. The egg was dropped on rice from the smash height. The egg has no noticeable damage. 6a. The egg makes an indent about .5 cm into the rice. 7a. Egg #1, when dropped from the smash height, is completely smashed. Egg #2 is aided by the cushion-properties of the rice, which slows down the speed of the egg at a rate slower than the table, and "giving" a little by making an indent. 8. The egg dropped into the padding didn't brake because it had a longer distance to stop.

Classwork 2/28
Calculate the force exerted on the egg if it is dropped from a height of 95cm and compressed a bowl of rice .5cm. The mass of the egg is equal to 55g. A falling egg has kinetic energy. To stop the egg, its KE must be taken away. It takes work to change the kinetic energy of an object. (W=DeltaKE) Fd=KEfinal-KEinitial Fd=0-1/2mvi2 F=-mvi2 / 2d

Vf2=Vi2+2ad Vf2=0+2(-9.8m/s2)(-.95m) Vf=-4.3m/s

F=-mvi2 / 2d -(.055kg)(-4.3m/s2)2 / 2(-.05m) = 10N

Checking Up
1. Kinetic energy depends on the mass and the velocity of the object. 2. Work is equal to the change in Kinetic Energy, therefore it can increase or decrease it. 3. The greater the distance, the less force that is needed. 4. Work and Kinetic Energy are measured in Joules.

Physics To Go
Page 290, March 1st, 2011 1a. The mitt increases the stopping distance that a baseball has to stop, if there wasn't a mitt, the ball would exert a greater pressure because it would impact your bare hand. 1b. Jumping from a height and landing on the ground by bending your knees increases the stopping distance because your legs are touching the ground, but you have more room to stop because you are bending your knees. 1c. Bungee jumping increases your stopping distance because the rope stretches, slowly bringing you to a stop instead of having to stop right away. The stretch increases the stopping distance. 1d. A wrestling mat increases the stopping distance by putting another layer between a person and the floor. 2. The kinetic energy increases by a factor of 9. 3. The faster egg will travel further than the slower egg because it is traveling at a higher speed and therefore will require a longer distance to stop if the blanket exerts the same force for each egg. 4. Force 60J, Distance 1m Force 30J, Distance 2m Force 15J, Distance 3m 5. 6a. 9720J 6b. 9720J 6c. 194.4J 7. B 8. C
 * KE || Mass || Speed ||
 * 500J || 1000kg || 1m/s ||
 * 20,000J || 1000kg || 20m/s ||
 * 100,000J || 5000kg || 20m/s ||
 * 50,000J || 500kg || 10m/s ||
 * 30,000J || 1000kg || 30m/s ||

=Section 4=

What Do You See?
Page 292, March 2nd, 2011 I see a car getting rear-ended by a truck. I see the dummy driver's head swinging back and getting hit. This is known as whiplash. The back of the car is smashed, it is a crumble zone. The rear-wheels of the car is in the air because the truck has a lot of inertia and continues to move through the car.

What Do You Think?
Page 292, March 2nd, 2011 Whiplash is when your head is suddenly jerked and hits an object. It is more prominent in rear-end collisions because when hit from behind your body moves forward and your head stays in place, leading it to be hyperextended backwards causing injury.

Checking Up
Newton's Second Law of Motion is if a body is acted upon by an unbalanced force, it will accelerate in the direction of the unbalanced force. Whiplash is the name for a type of neck injury to muscles of the neck typically as result of a car crash.

Physics Talk
1. A head rest and seat belts. 2. A force, such as another car in a collision pushes the car forward, but the body remains where it was, so the car pushes the rest of your body while your neck stays in the same spot. 3. A car is stationary (1st). The car is hit, and moves forward, the seat supports the body (2nd). The driver's head is stationary, and wants to stay there (1st). The head snaps forward (2nd). The head stays forward (1st). The neck muscles snap back.

Physics To Go
1. A car gets hit in a rear-end collision so it moves forward. Since your body is at rest it wants to stay at rest. However it is pushed forward by the seat and headrest, and your head will move backward. 2. The boxes in the truck are moving at the same speed of the truck. When the truck slows down, the boxes stay at the same speed that the truck was moving at. However they have no way to stop on their own. 3. Newton's first law, since the bus moves forward, and your body wants to stay at rest, so your body pushes against the seat. 4. Since there is no back support, you would get tossed around. 5. I think that headrests are beneficial in rear-end collisions as they prevent the neck from snapping backwards and help to slow it down. 6. Things such as headrests, better bumpers, more durable seats. 7. It prevents the neck from snapping backward.

=Section 5=

What Do You See
Page 304, March 7th, 2011 I see a small go-kart getting in a rear-end collision with a large truck. The go-kart's rear wheels are off the ground, which indicate that it is a collision. No noticeable change is seen in the large truck, as the go-kart is too small and moving at too slow of a speed to have any impact.

What Do You Think?
Page 304, March 7th, 2011 The factors that contribute to a collision are weight and speed, as these contribute to the force at which the cars are moving at. The driver of the small sports car will sustain greater injuries as his car is smaller, and is probably more likely to have greater damage.

Investigate
Page 304, March 8th, 2011 2a. The cart moving stops, and the stationary one begins movement at a higher speed. 3a. The cart moves away with a larger speed. 3b. The speeds were higher. 3c. A car being rear-ended at a red light. 5a. The stationary car moves with a higher velocity. 5b. Smart car being hit by a pickup truck. 5c. No, they are the same. 6a. The light car moves backwards and the heavy car moves backwards at a slower speed. 6b. Smart car crashing into a pickup truck. 6c. As the speed increases, the small car goes backward faster. 7a. The one that goes backward farther is the lighter one. 7b. We were right.

Physics Talk
Page 306, March 8th, 2011 The momentum of an object is defined as mass times velocity. P=mv. A small cart hitting a small cart is the same as a large cart hitting a large cart. Large objects have a large momentum because of their mass and small objects have a large momentum because of their speed.

Checking Up
Page 307, March 8th, 2011 1. An eagle would have more momentum because the eagle would have more mass than a butterfly. 2. The momentum is passed on from one object to another through contact. 3. The skateboarder would go flying because the car has more mass and most likely more velocity than a skateboarder.

Physics To Go
Page 309, March 8th, 2011 1. The car that was moving will transfer its energy to the stationary car, the car moving will end up stationary. 2. Both cars should stop. 3. The smaller car will move backwards at a faster rate. 4. It is harder to stop when running at a fast speed, they can tackle harder. 5. Whichever has the most momentum. 6. 1 m/s

=Section 6=

What Do You See
Page 310, March 8th, 2011 I see a red cart rolling down a ramp and rear-ending a blue cart. The carts both have crash dummies in them. People on the side are measuring time and distance, indicating they are probably calculating velocity and then momentum.

What Do You Think
Page 310, March 8th, 2011 Crash investigators probably use physics concepts such as momentum and velocity to judge how fast a vehicle was moving in a crash or how hard it impacted another car.

Investigate
Page 310, March 15th, 2011 2a.

3b. 3c. Total momentum before- 815 Total momentum after- 695 3d. The momentum decreases after the collision.
 * Mass of Object 1 (kg) || mass of Object 2 (kg) || Velocity of Object 1 Before Collision (m/s) || Velocity of Object 2 Before Collision (m/s) || Mass Combined Objects After Collision (kg) || Velocity of Combined Objets After Collision (m/s) ||
 * 250 || 250 || .71 || 0 || 500 || .32 ||
 * 500 || 250 || .6 || 0 || 750 || .34 ||
 * 750 || 250 || .45 || 0 || 1000 || .28 ||
 * Before the Collision ||  || After the Collision ||
 * Momentum of Object 1 kg (m/s) || Momentum of Object 2 kg (m/s) || Momentum of Combined Objects 1 and 2 kg (m/s) ||
 * 177.5 || 0 || 160 ||
 * 300 || 0 || 255 ||
 * 337.5 || 0 || 280 ||

Physics Talk
Page 312, March 14th, 2011 Law of conservation of momentum is an important part of physics. This means that the total momentum stays the same, or is conserved. The law of conservation of momentum helps us explain collisions between objects.

Checking Up
Page 315, March 14th, 2011 1. The amount of momentum is the same before and after a collision. 2. In a collision the momentum goes in the same direction as that of the force. In an explosion the momentum expands in all directions from the source of the explosion. 3. The total momentum will be 6000 kg-m/s, it has to have the same momentum as it had before the collision.

Physics To Go
Page 319, March 15th, 2011 1. If the first vehicle is traveling at a speed of 10m/s, when it collides with the second vehicle the two "stick" together and move off in the same direction at a speed of 5m/s. (---) > (---) >(---)(---) at 5m/s 10m/s 0m/s 2a. One car is moving at 2m/s and the other is moving -2m/s, because in order to move in opposite directions the momentum would need to be opposite. (---) ---> <--- (---) 2m/s - 2m/s <--- (---) (---) > 2m/s - 2m/s 2b. p=mv p=(1kg)(2m/s) p=2kg-m/s 2c. p=mv p=(1kg)(2m/s) p=2kg-m/s 3. 8m/s 4. The momentum is transferred from one car (loses momentum) and transfered to the other (gains). 5. There is no change in momentum, and the other vehicle will gain 4000kg-m/s. 6. 3m/s+2m/s=5m/s 5/2=2.5m/s 7. The player is moving 8.22m/s in the same direction as the person who bumped him. 8. -4m/s 9. M(A)V(A)i + M(B)V(B)i = M(A)V(A)f + M(B)V(B)f (45)(0)+(75)(0)=(45)(2)+(75)V 0=90+75V -90=75V V=-1.2 m/s 10. M(A)V(A)i + M(B)V(B)i = M(A)V(A)f + M(B)V(B)f (0.35)(20)+(0.06)(-30)=(0.35)(10)+(0.06)V 7+(-1.8)=3.5+0.06V 5.2=3.5+0.06V 1.7=0.06V V=28.3 m/s 11. M(A)V(A)i + M(B)V(B)i = M(A)V(A)f + M(B)V(B)f (3)(0)+(1)(4)=(3)(2)+1V 4=6+1V -2=1V V=-2 12. M(A)V(A)i + M(B)V(B)i = M(A)V(A)f + M(B)V(B)f (90)(0)+(0.16)(30)=(90)V+(0.16)(0) 4.8=90V V=0.053 m/s 13. M(A)V(A)i + M(B)V(B)i = M(A)V(A)f + M(B)V(B)f (45)(1.1)+(0.08)(0)=(45)V+(0.08)V 49.5 = 45.08V V=1.098 m/s 14.M(A)V(A)i + M(B)V(B)i = M(A)V(A)f + M(B)V(B)f (1700)(10)+(25)M=(1700)(-5)+(3.75)M 17000+25M =-8500+3.75M 25500=-21.25M M=-1200 kg M=1200 kg  15.M(A)V(A)i + M(B)V(B)i = M(A)V(A)f + M(B)V(B)f 16.M(A)V(A)i + M(B)V(B)i = M(A)V(A)f + M(B)V(B)f

=Section 7=

What Do You See Page 321, March 17th, 2011 I see a car with a crash test dummy approaching a barrier, but there are two "feet" that are giant springs located in the front of the vehicle. The springs act to give the car a longer stopping distance, allowing the car to stop without major damage to the vehicle itself and occupant. On the side there is a dog running and another dummy taking notes of his observations.

What Do You Think Page 321, March 17th, 2011 I think that vehicle engineers take into account a variety of factors when creating a crumple zone. Such as the speed the car will be traveling at, where the car is most likely to crash, the safety of the occupants in relation to where to put the crumple zone in the car.

Classwork 3/23 Impulse=(F)(T) (F)(T)=Change in momentum (F)(T)=(M)(Change in Velocity)

Physics Talk Page 324, March 23rd, 2011 W=(F)(D)=Change in KE.C You can maximize time and minimize the force, creating a safer collision. Creating a crumple zone helps to maximize time. Newton's second equation shows how much force is needed to stop a vehicle. F=ma, Force=(mass)(acceleration). You can rewrite Newton's Second Law as F=(Mass)(Change in Velocity)/(Change in Time). A change in momentum is known as an impulse. A large force over a small amount of time has the same impulse as a small force over a large amount of time. Momentum is equal to mass times velocity. The change in velocity of a person landing on grass will be the same as falling on concrete. However, the time is shorter on concrete, which is why it would cause greater injuries than grass. When a time gets longer, the denominator gets larger, which makes the force smaller. A small distance and great force creates a F-T graph that has a large vertical spike. But a large distance and small force creates a F-T graph that has a long horizontal spike. In a collision momentum is always conserved.

Checking Up Page 329, March 23rd, 2011 1. A crumple zone is a part of the car that intentionally deforms and "crumples" during an accident. The premise of this is to extend the amount of time the car has to stop and in effect putting less force on the occupants of the vehicle. 2. It is safer to collide with a soft surface rather than a hard one because the soft surface would have more "give" to it which would give the vehicle more time to stop. The hard surface would ensure that the vehicle stopped in as little time as possible, putting the occupants at greatest risk. 3. Momentum is the product of the mass and the velocity. 4. Momentum is mass times velocity, impulse is the change in momentum.

Physics To Go Page 332, March 23rd, 2011 1. Impulse is when a vehicle comes to a stop, it is stopped by an unbalanced force. 2. A crumple zone allows a vehicle to have more time to stop which exerts less force on the occupants. 3a. A padded dashboard is better because it allows for a greater time for the persons head to stop. 3b. The time is higher so the force will be lower. There will be less injury. 4. Your legs bending give you more time to slow down which causes less force to be exerted on your legs. 5. Your head has more time to slow down, so less force is exerted. 6a. 120 N 6b. 60 N 7. F = ma 10,000 / 1200 a= 8.3 8.3 = Delta(V)/(T) Delta(V) = 9.96 8. a = Delta(V)/Delta(T) a = (-5)/(0.1) a = -50 m/s F = ma F = (1500)(-50m/s) F = 75,000 9. The breakaway pole gives more time to slow down, so it causes less force and less injury. 10. There is more time in the one, so the graph is higher vertically, this means it has a smaller force.