Unit2_bruns

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Work and Power
**potential energy** || * energy possessed by an object because its above or below the zero level **energy** || * energy possessed by an object due to compressed or stretched spring || EPE || Joules || EPE= 1/2kx 2 k= spring force constant x= distance of stretching || stretched or compressed spring ||
 * **Term** || **Definition** || **Symbol** || **Units** || **Equation** || **Cue** ||
 * **work** || * caused by a force acting on axis of direction of motion
 * must be force
 * force must be in direction of motion
 * object must actually move
 * if force and direction are perpendicular, then it is not work
 * if a desk is pushing you and your pushing back that's still work
 * GAIN ENERGY--gravitation potential energy || capital W || Joules || W= Force *distance * cos phi || N, T, or f along axis of motion ||
 * **Kinetic Energy** || * energy due to an object moving || KE || Joules || KE= 1/mv 2 || object is moving ||
 * **Gravitational**
 * relative to where you make zero || GPE || Joules || GPE= (mg)height || location is above or below zero position ||
 * **elastic potential**

** definition: **
 * energy cannot be created or destroyed
 * it is transferred

initial energy + work= final energy KEi + GPE + EPEi + Win/out = KEf + GPEf + EPEf
 * MUST GO THROUGH AND CROSS OUT WHAT IS NOT THERE**

Lab: Air bags
__Objective:__ How does an air bag protect you during an accident? __Hypothesis:__ An air bag decreases the amount of force exerted on an object. For example, if a car hit a pole, the force from the pole and the car would be less when the airbag came out. __Materials:__ List any materials used and draw a labeled diagram of your set-up (alternatively, include a snapshot or video).

__Procedure:__
 * 2 eggs
 * flour
 * meter stick
 * bowl
 * 2 plastic bags

//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 length of your egg #1. Measure the mass of your egg. Record this information.
 * 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.
 * 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?
 * 6) Fill a bowl with flour and place the bowl inside of the box lid.
 * 7) Measure the length of your egg #2. Measure the mass of your egg. Record this information.
 * 8) Drop the egg from the smash height (Step 5). Measure the amount of egg sticking up out of the flour bed. How much of the egg is buried in the flour? Also, record your qualitative observations.
 * 9) Repeat this, increasing the height in 5-cm increments until the egg is cracked, and then smashed.



__Calculations:__ Show a sample for each, with equation(s), numbers plugged in, and answer with correct units.
 * What is the initial gravitational potential energy?
 * GPE=mgh
 * .0541 * 9.8 * .25= .132 J
 * How much work is done in each trial?
 * W=fd (cos phi)
 * .127.72 *25(cos 180)
 * How much force was used to stop the egg in each case?
 * F=mgh/d
 * .05213(9.8)(.05)/ .001

__Questions:__


 * 1) This investigation is an analogy for a person in an automobile collision. What does the egg represent? What does the table represent? What does the flour represent? **The Egg represents the person or their head. The flour represents the airbags. The table probably represents the point of impact the car is at.**
 * 2) Define the terms: Gravitational Potential Energy, Kinetic Energy and Work. ** GPE is energy possessed by an object because its above or below the zero level. Kinetic energy is energy due to an object moving. Lastly, work is caused by a force acting on axis of direction of motion, force must be in direction of motion not perpendicular.**
 * 3) What factors determine an object's kinetic energy? **The factors determining an objects kinetic energy are the velocity and mass.**
 * 4) When work is done on an object, what is the effect on the object's kinetic energy? **When work is done on an object, the energy could either be gained or lost**
 * 5) How does the force needed to stop a moving object depend on the distance the force acts? **The force needed to stop moving an object depends on the distance the force acts because by making the distance longer, the force needed to stop the moving object is less because you have a longer time.**
 * 6) What difference does a soft landing area make on a passenger during a collision? ** There will be less damage on the person and less force being exerted on the car. **
 * 7) How does a cushion reduce the force needed to stop a passenger? ** A cushion helps you by not hitting harder parts on the car. and less force on the passenger. For example, by using the air bag as a cushion, you are hitting a softer thing that has less force, instead of hitting something extremely hard like a steering wheel. **
 * 8) What does the law of conservation of energy have to do with this? ** This has to do with energy cannot be created or destroyed, it is transferred. It is transferred because the force from having the collision to when you crash transfers the energy to the passengers in the car and puts the force on them. **

__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. **The law of conservation of energy is defined as energy cannot be created or destroyed, but it is transferred. The energy is transferred because when you're in an accident and the air bags come out, it gives you more time so that there is less of an impact. The air bags would save you from hitting your head maybe on the steering wheel, increasing the amount of time and giving you damage on your body, but less damage if there were no airbags and there wasn't cushioning.**
 * Explain at least 1 cause of experimental error. Be sure you describe a specific reason. ** It was really difficult to measure how much of an impact the egg made on the flour. When the egg would land in the flour. it was hard to distinguish the measurements because the egg didn't land the same exact way every time. You also had to ** **put the meter stick in flour but you didn't know whether or not you were sticking it in the flour or at the right point.**
 * 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?) **I believe that we could change the bowl to some sort of pan and then fill it with flower. It would be a lot easier to also not use a meter stick because it is so big. Finally, since it was hard to be accurate with the dropping point, we could have a shelf where the egg exactly goes off into the flower.**

**Homework lesson 17 and 18**
Internal External positive work gain energy negative work lose energy **what is the relationship between work and energy?** KEi + PEi + Wext = KEf + PEf
 * What are internal/external forces? How do we categorize them? How do you determine whether there is an internal/external force? **
 * based on whether or not their presence is capable of changing an object's total mechanical energy**
 * gravity forces
 * magnetic force
 * electrical force
 * spring force
 * applied force
 * normal force
 * tension force
 * friction force
 * air resistance force
 * Can be a positive or negative work term

**How do you make bar chart illustrations?** 1. analyze the initial and final states of the object, make decisions about the presence or absence of the different forms of energy 2. analyze the forces acting on the object during the motion to determine if there are external forces and if the work is positive or negative 3. construct bars on the chart to show the presence and absence of the various forms of energy for the initial and final state of the object 4. the exact height of the individual bars is not important 5. important is that the sum of the heights on the left of the chart is //balanced by// the sum of the heights on the right of the chart
 * What is the equation for mechanical energy conserved? How does pendulum motion relate? **
 *  KEi + PEi + Wext = KEf + PEf
 *  Simplified equation: KEi + PEi = KEf + PEf (here it is conserved)
 *  Gravity (an internal force) acts downward and the tensional force (an external force)
 *  Kinetic energy gained

**What is potential energy and GPE ? What is the relation between GPE and an object? What about the relation of GPE and height of an object?** **What is EPE?** **What is mechanical energy? What is the equation?** <span style="color: #ffcf00; font-family: 'Times New Roman',Times,serif; font-size: 16px;">**What is power? What is the equation?** [|work energy and power video]
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;"> Potential energy-stored energy of position possessed by an object
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;"> GPE-energy stored in an object as the result of its vertical position or height, the result of the gravitational attraction of the Earth for the object
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;"> relation between gravitational potential energy and the mass of an object- More massive objects have greater gravitational potential energy
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;"> direct relation between gravitational potential energy and height of an object- The higher that an object is elevated, the greater the gravitational
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;">potential energy equation: PEgrav = mass • g • height
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;">energy stored in elastic materials as the result of their stretching or compressing (relative due to some zero position)
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;">the more stretch, the more stored energy
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;">PEspring= 1/2kx2 k- is spring constant x- compression
 * <span style="color: #ffcf00; font-family: 'Times New Roman',Times,serif; font-size: 16px;">What is kinetic energy? What is the equation? **
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;"> energy of motion
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;"> vibrational, translational, rotational energy
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;"> KE=1/2 mv2 m= mass, v=speed of object
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;"> kinetic energy of an object is directly proportional to the square of its speed
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;"> for an increase in speed, basically the square of the original for kinetic energy
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;"> 1 joule= 1 kg*(m/s)2
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;"> The energy acquired by the objects upon which work is done
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;"> in motion and/or if they are at some position relative to a zero potential energy position
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;"> TME = PEgrav + PEspring + KE (total energy)
 * rate at which work is done
 * power= work/time
 * w= often the GPE or KE
 * unit of power= watt
 * rate of energy usage

[|Work energy theorem using horsepower]

<span style="color: #b4ff00; display: block; font-family: 'Comic Sans MS',cursive; font-size: 200%; text-align: center;">Momentum, Impulse
momentum= m * v directly proportional
 * name || Equation || Units ||
 * Momentum || p= m*v || kg m/s ||
 * Impulse || Net force (contact)= mv || J ||

<span style="color: #00ff76; display: block; font-family: 'Comic Sans MS',cursive; font-size: 180%; text-align: center;">Lab: Momentum and elastic Collisions
__Objective:__ A small sports car hits a heavy truck in a collision. What factors determine the outcome for the passengers of the two vehicles? Which driver will sustain worse injuries? Why? definition: when KE is conserved __Materials:__ List any materials used and draw a labeled diagram of your set-up (alternatively, include a snapshot or video). __Procedure:__
 * 2 carts
 * different grams of blocks
 * 1) Place a cart on the middle of the track with the spring to the right. On a piece of masking tape, label this the "Target cart." Place a second identical cart on the right end of the track. Mark this as the "Bullet cart".
 * 2) Push the bullet cart very gently towards the target cart so that they collide, with the spring between them.
 * 3) Repeat step 2 several times, giving the bullet cart a bigger push each time. Record your observations.
 * 4) Add 500-g to each cart and repeat the process. Record your observations and compare the results to the first set of collisions.
 * 5) Remove the mass from the target cart and repeat the above steps.
 * 6) Add the mass to the target cart and remove the mass from the bullet cart, and repeat.
 * 7) Get the "Mystery" cart from your teacher. Determine the relative mass of the cart by putting it through a sequence of collisions.

__Data and observations:__


 * Mystery Weight 1:** The weight is approximately 350-400 grams because our bullet cart moved a small amount when we used both the 400 gram weights and the 300 g weight.


 * Mystery Weight 2:** The weight is approximately 600-700grams because our bullet cart moved a small amount when we used both the 700 gram weights and the 600g weight.

__Questions:__
 * 1) What is a real-life collision that the collisions in this investigation could represent? **A real life collision that this investigation could represent is bumper cars hitting each other.**
 * 2) How well did observing collisions enable you to compare the masses of the carts in the last step? **Observing the collisions enabled me to investigate the masses of the carts. We were not far off in the mystery weights. Mystery weight 2 shows between 600-700 grams which came out to be correct because the mystery weight was 700 grams. Mystery weight one that we had was approximately 400 grams, showing that our guess was very close between 350-400 grams.**
 * 3) What happened after the collision as the masses changed? **When the mass of the bullet cart was more than the target cart, the amount of distance and speed changed to make it quicker, showing that the force momentum transferred was bigger. Whereas, if the masses were the same, there would be the same reaction with the bullet and target cart.**
 * 4) Define the term momentum. **Momentum is the quantity of motion that an object has. It can also be described as "mass in motion".**
 * 5) Which object has greater momentum, a butterfly traveling at 16 km/h or an eagle traveling at the same speed? **An eagle has a greater momentum. He would have the greater momentum because momentum doesn't solely rely on velocity, but also mass. An eagle would have a greater mass than a butterfly.**
 * 6) How does the transfer of momentum occur? **The transfer of momentum occurs when 2 objects collide.**
 * 7) Use momentum to describe what would happen if a skaterboarder was hit by a car. **If a skateboarder was hit by a car, the cars momentum would be transferred to the skateboarder putting more force on the skateboarder and causing him to be pushed back into the opposite direction.**

__Conclusion:__ · Based on the relative amounts of momentum, what is the outcome of a head-on collision between a heavy truck and a small sports car if both have the same speed? **In this situation, the small sports car would be more damaged and the heavy truck would have less damage. Because the both have the same speed, does not mean that they are both going to have an equal amount of momentum. A heavier truck would have a bigger momentum because its mass would be greater than the mass of the small sports car.** · Explain at least 1 cause of experimental error. Be sure you describe a specific reason. **One reason could be the definition of the applied force. We only used qualitative only which just shows us looking at the cart colliding with our naked eye. We cannot tell what is an average applied force and a fast applied force.** · 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?) **I would add a photogate timer to show the times of the collisions. Maybe by adding my mass shows that there could be a correlation between the time and mass showing that if the mass is more, there is more time. Also, i would try and measure the applied force between the bullet and target cart. just saying there is a low, average, or fast applied force doesn't represent HOW MUCH force there is.**

<span style="color: #b4ff00; display: block; font-family: 'Comic Sans MS',cursive; font-size: 200%; text-align: center;">LCM- law of conservation of momentum
<span style="display: block; height: 1px; left: -10000px; overflow: hidden; position: absolute; top: 3623px; width: 1px;">__Objective__: What physics principles do the traffic-accident investigators use to "reconstruct" the accident? <span style="display: block; height: 1px; left: -10000px; overflow: hidden; position: absolute; top: 3623px; width: 1px;">__Procedure:__
 * momentum cannot be created or destroyed but can be transformed
 * total momentum of a system remains constant, as long as the system is isolated (ignore friction during collision)
 * sum of the initial momentum has to be equal to the sum of the final momentum
 * equation: m1v1 initial + m2v2 initial= m1v1f + m2v2 final

<span style="color: #00ffdb; display: block; font-family: 'Comic Sans MS',cursive; font-size: 220%; text-align: center;">Lab: Inelastic Collision
<span style="display: block; height: 1px; left: -10000px; overflow: hidden; position: absolute; top: 3623px; width: 1px;">__Conclusion:__ <span style="display: block; height: 1px; left: -10000px; margin-left: 0.5in; overflow: hidden; position: absolute; text-indent: -0.25in; top: 3623px; width: 1px;"><span style="font-family: 'Tahoma','sans-serif'; font-size: 7pt;">• Based on the law of conservation of momentum, how can the traffic-accident investigators use this to "reconstruct" an accident? What does it mean to "conserve" momentum<span style="font-family: 'Tahoma','sans-serif'; font-size: 7pt;">• Explain at least 1 cause of experimental error. Be sure you describe a specific reason.<span style="font-family: 'Tahoma','sans-serif'; font-size: 7pt;">• 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?
 * definition:** when KE is __NOTTTTTTTT__ being conserved
 * __Objective__:** How does the initial momentum compare to final momentum?
 * __Hypothesis__:** Initial momentum is going to be the same as the final momentum.
 * __Procedure:__**
 * 1) Place 2 photogates on a track, one at 50 cm and the other at 75 cm. Hook these into a Smart Timer and set the Smart Timer to Velocity.
 * 2) Place a cart so that its end is at 75 cm (right in front of the photogate), with the velcro facing 0-cm. Call this the "target cart." Place a second identical cart at the end of the track closest to 0-cm. Call this the "Bullet cart". Make sure that both carts have picket fences.
 * 3) Click "Start" on the Smart Timer, 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.
 * 4) Record the velocity right before (the Bullet Cart initially) and right after the collision (the two carts linked). Record these values in your data table.
 * 5) Vary the masses of the carts and repeat the process 5 times.


 * __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.
 * 5) Find the percent difference between the initial momentum (calc 3) and the final momentum (calc 4).

__Questions:__
 * 1) How do the initial momenta compare to the final momenta? Allowing for minor variations due to uncertainties of measurement, are there any patterns? The initial momenta compared to the final momenta is almost equal to each other. The final momenta was off about .02 - .04 from all the initial momentum of the bullet cart. There are not really any patterns, but the numbers are almost exact comparing the final momenta to the initial momentua
 * 2) Which types of collisions are definitely inelastic? How do you know? An inelastic collision is when kinetic energy is not being conserved. It occurs when 2 objects collide and they do not bounce off away each other.
 * 3) Which types of collisions are definitely elastic? How do you know? Elastic collisions is when no kinetic energy is lost in a collision. You know this because when two objects collide, they bounce apart. Specific example: 2 bouncy rubber balls.
 * 4) 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. In the law of conservation of momentum, the initial momenta has to be equal to the final momenta.  Momentum can also not be created or destroyed but transformed. Therefore, when a cue ball hits the 15 balls in the middle of a pool table, to find the momentum its mass x velocity which creates the force acting upon the 15 balls makes the balls go in all different directions.

__Conclusion:__
 * Based on the law of conservation of momentum, how can the traffic-accident investigators use this to "reconstruct" an accident? Traffic-accident investigators use the law of conservation of momentum because we know that the total momentum remains the same, but the individual momenta stays the same. Traffic investigators can determine the initial velocity of the vehicles to understand what the collision would look like. What does it mean to "conserve" momentum? By conserving momentum, it is meant that the initial momentum and final momentum is going to be the same.
 * Explain at least 1 cause of experimental error. Be sure you describe a specific reason. One experimental error could have been the photogate timers. Sometimes they are not always accurate. Sometimes the carts don't go through the photogate all the way. Also, the cart isn't pushed at the same constant speed every single time you push it through the photogate.
 * 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?) Overall, I thought that all my results were really accurate, and nothing really went wrong. Otherwise if there was a problem, i think the consistency of speed pushing through the photogate timer could have been more accurate.

<span style="color: #00a1ff; display: block; font-family: 'Comic Sans MS',cursive; font-size: 190%; text-align: center;">Homework 19 and 20:
Momentum topic sentence: <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;">Momentum is a vector quantity which is defined as the quantity of motion that an object has using the equation Momentum = mass • velocity with the units kg m/s. <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px;">Impulse topic sentence: <span style="font-family: 'Times New Roman',Times,serif;"> Related to Newton’s second law of the acceleration of an object is directly proportional to the net force acting upon the object and inversely proportional to the mass of the object, impulse is the quantity Force • time described with the equation as F • t = m • Δ v.

Momentum conservation principle: In the momentum conservation principle, it is defined as total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision which implements Newton’s third law. f1= -f2 show the forces are equal in magnitude and opposite in direction.

System Topic Sentence: A system is a collection of two or more objects. An isolated system is a system that F is free from the influence of a net external force that alters the momentum of the system. In order for there to be a net external force, there must be a force that is not balanced by other forces and a force that originates from a source other than the 2 objects.

Constant Momentum: The constant momentum equation is m1v1 + m2v2= m1v1final + m2v2final. When using this equation if there is a twofold increase in mass, results in a twofold decrease in velocity (the velocity is one-half its original value) and if it’s a threefold increase in mass results in a threefold decrease in velocity (the velocity is one-third its original value).

[|law of conservation of momentum video] [|Impulse momentum theory video]