On
Monday classes reviewed potential and kinetic energy with equations
and notes. Last Tuesday classes had an assignment due; it was assigned the
previous Thursday – p.133#1-7. Tuesday we also watched a video and
discussed it – relating car crashes and vehicle safety to principles we’ve
discussed in class, and related Gs of
acceleration to force experienced in car wrecks and other situations,
and yesterday we had notes on various forms of potential energy.
Today in class we
worked a practice worksheet and discussed what happens to Kinetic
energy when velocity of an object changes. If not finished in class today, it's homework and due tomorrow.
New Optional Assignment (discussed in class Monday) Use safercar.gov to research a car you ride in often, and then find a safer car and a more dangerous car from the same model year. Using terms we discussed in class or information you learn on safercar.gov, explain possible reasons for the higher and lower safety ratings. Turn in no later than December 14.
Tuesday, November 29, 2011
Friday, November 18, 2011
More Energy!
Highlights from class today:
GPE / KE in different locations with a pendulum (see reading assignment from yesterday - due tuesday for an example)
Evaluation / definition / units of work: a force applied to an object for a distance. Units: N*m or Joules (J)
Other equations:
GPE = m*g*h
KE= 1/2*m*v^2
and examples...
GPE / KE in different locations with a pendulum (see reading assignment from yesterday - due tuesday for an example)
Evaluation / definition / units of work: a force applied to an object for a distance. Units: N*m or Joules (J)
Other equations:
GPE = m*g*h
KE= 1/2*m*v^2
and examples...
Thursday, November 17, 2011
E is for Energy, R is for Robot
HMWK (Due Next Tuesday) Read p. 128-133, p. 133#1-7
Announcement: Robotics Club will meet Thursdays; 2:30 - 4:30. If you can make that time (or part of that time) work, please get an application and $12 to Mr. Freeman by Monday. 1st "hands-on" meeting is the Thursday after Thanksgiving.
Today in class: Conservation of Energy: repeated some of Galileo's experiments, one with ramps and balls, and the other with a giant pendulum.
Basic ideas:
If you release a ball from one side of an unevenly curved ramp surface (think a skateboarding halfpipe that's uneven), the distance the ball rolls up the other side is not necessarily equal to the distance rolled down.... what DOES matter is the height. The ball will roll up to approximately the same height as it was released from. The same holds true with a pendulum; it will return to approximately its release height. Galileo used this to coin the idea of the Law of Conservation of Energy (from this point on, we'll refer to Energy as just E )
Two parts exist to the Law of Conservation of E. 1. E can't be created or destroyed. 2. E transferrs between different forms and objects.
A good time to review scientific laws vs. theories;
A law states what happens. (ex. Energy doesn't appear or disappear - it has never been shown to happen) (gravity: objects fall down, or objects are attracted to one another, proportional to their mass and distance between them)
A theory explains why/how something happens. Theories of gravity exist as maybe involving a particle, or maybe being actually connected to electricity and magnetism in some way that hasn't been discovered yet. Mass is theorized to be actually the same thing as energy. Maybe we're all just made of bits of oscillating energy. (etc.)
Finally, two big types of energy: GPE (Gravitational Potential Energy) = energy stored by an object's position in a gravitational field
KE (Kinetic Energy) = energy in a moving object.
Announcement: Robotics Club will meet Thursdays; 2:30 - 4:30. If you can make that time (or part of that time) work, please get an application and $12 to Mr. Freeman by Monday. 1st "hands-on" meeting is the Thursday after Thanksgiving.
Today in class: Conservation of Energy: repeated some of Galileo's experiments, one with ramps and balls, and the other with a giant pendulum.
Basic ideas:
If you release a ball from one side of an unevenly curved ramp surface (think a skateboarding halfpipe that's uneven), the distance the ball rolls up the other side is not necessarily equal to the distance rolled down.... what DOES matter is the height. The ball will roll up to approximately the same height as it was released from. The same holds true with a pendulum; it will return to approximately its release height. Galileo used this to coin the idea of the Law of Conservation of Energy (from this point on, we'll refer to Energy as just E )
Two parts exist to the Law of Conservation of E. 1. E can't be created or destroyed. 2. E transferrs between different forms and objects.
A good time to review scientific laws vs. theories;
A law states what happens. (ex. Energy doesn't appear or disappear - it has never been shown to happen) (gravity: objects fall down, or objects are attracted to one another, proportional to their mass and distance between them)
A theory explains why/how something happens. Theories of gravity exist as maybe involving a particle, or maybe being actually connected to electricity and magnetism in some way that hasn't been discovered yet. Mass is theorized to be actually the same thing as energy. Maybe we're all just made of bits of oscillating energy. (etc.)
Finally, two big types of energy: GPE (Gravitational Potential Energy) = energy stored by an object's position in a gravitational field
KE (Kinetic Energy) = energy in a moving object.
Wednesday, November 16, 2011
Air Resistance - why/how?
We watched more videos to give examples and depth to our study of air resistance and had some notes on what influences air resistance. To sum it up:
Factors influencing air resistance:
-Size of object: greater size encounters more air - specifically the size of the object perpendicular to the direction of motion.
-Shape of the object: how air must move around the object and action-reaction forces involved in making air move
- Air density - more dense air --> more matter encountered by object per second
-velocity of object relative to air - more difference in velocities --> more matter encountered by object per second.
We analyzed air resistance of a falling object until velocity increases to equal gravity's pull: terminal velocity, when acceleration = 0 and the object falls at its maximum, constant velocity.
Much discussion was involved in different classes:
Skydiving to break the sound barrier and a world record (apparently hasn't been broken yet)
Aptera - awesome aero, so why not in production yet? (some interesting conspiracy theories out there as to what the heck happened)
other fun aero cars
Factors influencing air resistance:
-Size of object: greater size encounters more air - specifically the size of the object perpendicular to the direction of motion.
-Shape of the object: how air must move around the object and action-reaction forces involved in making air move
- Air density - more dense air --> more matter encountered by object per second
-velocity of object relative to air - more difference in velocities --> more matter encountered by object per second.
We analyzed air resistance of a falling object until velocity increases to equal gravity's pull: terminal velocity, when acceleration = 0 and the object falls at its maximum, constant velocity.
Much discussion was involved in different classes:
Skydiving to break the sound barrier and a world record (apparently hasn't been broken yet)
Aptera - awesome aero, so why not in production yet? (some interesting conspiracy theories out there as to what the heck happened)
other fun aero cars
Tuesday, November 15, 2011
Robotics...and air resistance competition
Today all classes got to see an informational video regarding the FTC robotics team/competition we're trying to get started; I handed out forms to interested people and I will have a sign-up sheet tomorrow where you can show which day(s) you would be able to meet (for those with a serious interest). The cost of this competition is less than $20 from you - see me if for personal/family reasons you cannot afford this and are genuinely interested; I will find a way. We won't collect money for applications until we confirm on a weekly meeting day and time, so please discuss with your parents tonight.
Most students brought in objects that would maximize air resistance while minimizing weight; today we got to test them out in a competition with a winner from each class. Some students were able to find objects that would take the longest times to fall and beat their entire class; winning times are 5, 7, 9, and 14 seconds so far today.
Tomorrow we'll talk aerodynamic drag and watch some related videos, then do some discussion of how the concepts here relate to falling objects and cars moving through the air.
If you haven't finished the optional assignment yet, I will extend the due date; you may turn it in for full credit until next Tuesday.
Frankenstein Lab Part I is this Thursday in Mr. Kasey's room (314) 2:30-3:30. Very cool and fun - I highly recommend it.
Most students brought in objects that would maximize air resistance while minimizing weight; today we got to test them out in a competition with a winner from each class. Some students were able to find objects that would take the longest times to fall and beat their entire class; winning times are 5, 7, 9, and 14 seconds so far today.
Tomorrow we'll talk aerodynamic drag and watch some related videos, then do some discussion of how the concepts here relate to falling objects and cars moving through the air.
If you haven't finished the optional assignment yet, I will extend the due date; you may turn it in for full credit until next Tuesday.
Frankenstein Lab Part I is this Thursday in Mr. Kasey's room (314) 2:30-3:30. Very cool and fun - I highly recommend it.
Monday, November 14, 2011
MidTerm, Robotics, and air resistance challenge
After the midterm exam today:
Discussed opportunity to design and compete with robots; First Tech Challenge and new FHS robotics team. Need to get applications in soon to start building! http://www.usfirst.org/roboticsprograms/ftc
See me for more info.
ALSO: design a device to maximize air resistance... while minimizing weight; we will test tomorrow by dropping devices from the ceiling and competing for bonus points - the longest to reach the ground.
Discussed opportunity to design and compete with robots; First Tech Challenge and new FHS robotics team. Need to get applications in soon to start building! http://www.usfirst.org/roboticsprograms/ftc
See me for more info.
ALSO: design a device to maximize air resistance... while minimizing weight; we will test tomorrow by dropping devices from the ceiling and competing for bonus points - the longest to reach the ground.
Thursday, November 10, 2011
Wednesday, November 9, 2011
Midterm Monday
Today we watched a video to kick-off our interest and study in air resistance; if you want to watch the rest let me know and I would be happy to loan it out.
We also discussed answers to homework and full credit was given to anyone needing to correct their answers. Grades are posted now.
Finally, we discussed ways to study: I started with some techniques that I have employed in the past and we will look at others in the future:
1. re-write or explain your notes: use a separate journal and re-write (not just copy) notes from class. Rephrase in words that are yours; if you can't do this, the concept is either really simple and hard to reword, or you need help understanding it.
2. use flash cards - vocabulary terms are unlikely to bring you huge points in this class by themselves, but if you don't know the vocabulary inside and out, you will have little to no chance on the concept questions that use these terms. Use the chapters in your book as a guide; they highlight new vocabulary in the beginning of each section and highlight the terms in the text.
3. Work practice problems. These don't have to come from some mystical location; you've had lots of homework that's on-topic this semester. Look back at section review questions in your text, and if you can't find your graded or corrected homework, ask a friend or come see me to look at my answer key in my text. Chances are that you'll need a bit of review in the text or your notes to answer some of those problems.
4. Quiz yourself - make use of the online student resources from your textbook - you don't need an access code! See the front or inside cover of your text - it has "gpescience.com" written all over it for a reason. Scroll down to the "chapter activities" and select any of the links.. choose a chapter (1, 3, or 4) from the menu at the left, and try out:
-Chapter Review Quizzes
-Vocabulary eFlashcards
-Look at the bottom left menu and select different sections within the chapter to try out specific section/unit quizzes.
Tomorrow we'll be playing a competitive review game for a chance at a few bonus points. I will be grouping you against others who I think will be good competition. Should be fun!
We also discussed answers to homework and full credit was given to anyone needing to correct their answers. Grades are posted now.
Finally, we discussed ways to study: I started with some techniques that I have employed in the past and we will look at others in the future:
1. re-write or explain your notes: use a separate journal and re-write (not just copy) notes from class. Rephrase in words that are yours; if you can't do this, the concept is either really simple and hard to reword, or you need help understanding it.
2. use flash cards - vocabulary terms are unlikely to bring you huge points in this class by themselves, but if you don't know the vocabulary inside and out, you will have little to no chance on the concept questions that use these terms. Use the chapters in your book as a guide; they highlight new vocabulary in the beginning of each section and highlight the terms in the text.
3. Work practice problems. These don't have to come from some mystical location; you've had lots of homework that's on-topic this semester. Look back at section review questions in your text, and if you can't find your graded or corrected homework, ask a friend or come see me to look at my answer key in my text. Chances are that you'll need a bit of review in the text or your notes to answer some of those problems.
4. Quiz yourself - make use of the online student resources from your textbook - you don't need an access code! See the front or inside cover of your text - it has "gpescience.com" written all over it for a reason. Scroll down to the "chapter activities" and select any of the links.. choose a chapter (1, 3, or 4) from the menu at the left, and try out:
-Chapter Review Quizzes
-Vocabulary eFlashcards
-Look at the bottom left menu and select different sections within the chapter to try out specific section/unit quizzes.
Tomorrow we'll be playing a competitive review game for a chance at a few bonus points. I will be grouping you against others who I think will be good competition. Should be fun!
Tuesday, November 8, 2011
11-8 Friction Notes/ begin air resistance / HMWK
Don't forget tomorrow's HMWK: p. 123, #19-24, 27.
Also announced: Midterm will be next Monday and will cover content (more broadly than other tests) from the class so far this semester from measurement and scientific method to forces.
Today started with a question; if surface area is changed, friction doesn't change (on the average, over multiple trials). WHY? It seems like we learned that microwelds happen and cause friction where objects touch, so it makes sense for surface area to be a factor... and it is, sort of. MICROSCOPIC surface area is what counts, and it depends on the surface types and the force pushing the surfaces together. When surface area is changed on the macroscopic (what we can see) level, say by putting a box on its end, the weight of the object doesn't change... the pressure per unit area is greater, causing the box's surface to compress any tiny bumps within it, and microscopic surface area in contact actually remains the same as it was when the box sat normally. A student said his answer well today; "the microwelds in an area are more concentrated."
Today's notes:
Also announced: Midterm will be next Monday and will cover content (more broadly than other tests) from the class so far this semester from measurement and scientific method to forces.
Today started with a question; if surface area is changed, friction doesn't change (on the average, over multiple trials). WHY? It seems like we learned that microwelds happen and cause friction where objects touch, so it makes sense for surface area to be a factor... and it is, sort of. MICROSCOPIC surface area is what counts, and it depends on the surface types and the force pushing the surfaces together. When surface area is changed on the macroscopic (what we can see) level, say by putting a box on its end, the weight of the object doesn't change... the pressure per unit area is greater, causing the box's surface to compress any tiny bumps within it, and microscopic surface area in contact actually remains the same as it was when the box sat normally. A student said his answer well today; "the microwelds in an area are more concentrated."
Today's notes:
Friction
Force that opposes sliding motion
Friction:
n Affects objects in contact
n Opposes sliding forces up to a maximum
n Depends on the surfaces involved and the force pushing them together
What is friction caused by?
n Tiny bumps in all material come into contact
n Microwelds are formed
n Small attractive forces “bond” materials
n More force pushes materials closer together
n Leads to more microwelds
Types of Friction: Static Friction
n Surfaces not moving relative to one another
n Static Friction is the strongest type of friction.
Kinetic Friction
n Once in motion, objects don’t form as many microwelds.
n Results in lower frictional resistance
n Easier to keep something sliding than to start it.
Rolling and Friction
n Reduces sliding friction involved greatly
n Application – bearings – small cylinders or balls that surfaces roll over
n (wheels as well)
Calculating Frictional Force
n Frictional force =
force pushing surfaces together • coefficient of friction
A coefficient of friction is just a ratio (%) of force between surfaces that gets transformed into friction
Coefficients of friction:
μs = coefficient of static friction
μk = coefficient of kinetic friction
μ = greek letter mu (lower case) pronounced “myeou”
Practice problem 1:
n A 4N book is being pulled across a surface with a μk of 0.29. Find the frictional force.
Practice Problem 2
n A 10N textbook requires 8N of force to get it to start moving, and 6N to keep it moving. Find μs and μk
Monday, November 7, 2011
11-7 Friction as Centripetal Force, Present Lab Data
HMWK: p. 123, #19-24,27. Due Wednesday.
Today in class: Discussed how friction can act as a Centripetal (center-seeking) force if it is what keeps an object move in a curved path, such as a car moving around a corner, or you turning a corner in the hall: if there's not enough friction, you can't accelerate (you maintain the same speed and direction) which usually means bad things if you have some velocity that you were intending to change.
We also went over the work to answer questions from Friday that were on the board, and then allowed each group to present from their friction experiment: IV, Hypothesis, How it was tested, Observations, and Results to the class. Some of the more interesting findings were the effects of water on friction; in most of the tested situations, water actually increased frictional force. Some hypothesized that this was the result of a "suction cup" effect - probably the result of interesting chemistry surrounding water.
Be sure to see Friday's post for the new OPTIONAL ASSIGNMENT
Today in class: Discussed how friction can act as a Centripetal (center-seeking) force if it is what keeps an object move in a curved path, such as a car moving around a corner, or you turning a corner in the hall: if there's not enough friction, you can't accelerate (you maintain the same speed and direction) which usually means bad things if you have some velocity that you were intending to change.
We also went over the work to answer questions from Friday that were on the board, and then allowed each group to present from their friction experiment: IV, Hypothesis, How it was tested, Observations, and Results to the class. Some of the more interesting findings were the effects of water on friction; in most of the tested situations, water actually increased frictional force. Some hypothesized that this was the result of a "suction cup" effect - probably the result of interesting chemistry surrounding water.
Be sure to see Friday's post for the new OPTIONAL ASSIGNMENT
Thursday, November 3, 2011
Subscribe to:
Posts (Atom)