PhyFl18SS3.3.1 Taken right before the In House Preseason Tournament. There are at least a few future millionaires in this picture.
PhyFl18SS3.3.2 1st Semester Hall of Famers. Chosen by proven brilliance of mind.
PhyFl18SS3.3.3 Monday’s outline
PhyFl18SS3.3.4 Prob 3.7.2a
PhyFl18SS3.3.5 Prob 3.7.2a and 2b
PhyFl18SS3.3.6 Prob 3.7.3
PhyFl18SS3.3.7 Prob 3.7.3
PhyFl18SS3.3.8 Prob 3.7.3
PhyFl18SS3.3.9 Deriving the Blue Quad
PhyFl18SS3.3.10 Blue Quad
PhyFl18SS3.3.11 Sheet 3.3 (front)
PhyFl18SS3.3.12 Sheet 3.3 (Front) adding vectors
PhyFl18SS3.3.13 Sheet 3.3 (top of back)
PhyFl18SS3.3.14 Sheet 3.3 the back
PhyFl18SS3.3.15 Tuesday’s bullet points
PhyFl18SS3.3.16 3rd hours’s Rocket Launch data
PhyFl18SS3.3.17 6th hours’s Rocket Launch data
PhyFl18SS3.3.18 36th hours’s Rocket Launch data
PhyFl18SS3.3.19 percent difference between the two different techniques to determine launch velocity
PhyFl18SS3.3.20 7th hours rocket launch data
PhyFl18SS3.3.21 7th hours rocket launch data
PhyFl18SS3.3.22 VERY IMPORTANT! Shows acceleration vectors in green (with magnitudes = g) and the various velocity vectors of the rocket
PhyFl18SS3.3.23 Prob 3.7.6
PhyFl18SS3.3.24 A negative trio graph of Prob 3.7.6
PhyFl18SS3.3.25 Another example of a negative trio
PhyFl18SS3.3.26 An example of a positive trio
PhyFl18SS3.3.27 Wednesday’s bullet points
PhyFl18SS3.3.28 THursday’s bullet points
PhyFl18SS3.3.29 Prob 3.3 Back: Component Method and stack and rack
PhyFl18SS3.3.30 This is our class data from dropping the basketball from a the ceiling in the room (considered a small height) Small heights are any height where the time of fall is less than 1 second. The MAJOR problem with this time data is that it reduces down to 1 sig fig after you take into account the human reaction time (±0.15sec). One sig fig data is the death sentence in science. NOBODY will believe you.
PhyFl18SS3.3.36 Momentum is “moving inertia” We will study it in detail 2nd semester. Its the reason an object will keep on rising (but slowing down) after the upward force is removed. The object wants to keep going and going until the earth’s gravitational field gently calls it back home.
PhyFl18SS3.3.37 Prob 3.7.7
PhyFl18SS3.3.38 Prob 3.9.1 Vector PUZZLES!
PhyFl18SS3.3.39 We just mentioned the idea of MULTIPLYING vectors. Thats a second semester thing. Two ways to multiply vectors: Dot Products and Cross Products
PhyFl18SS3.3.40 Dot products are the source of all energy from forces. Cross Products are the source of all rotations and twists
PhyFl18SS3.3.41 . . . .
PhyFl18SS3.3.42 . . . .
PhyFl18SS3.3.43 These people take recorders to heights I have never heard before.
PhyFl18SS3.3.44 The Stella crowd was large on Saturday morning. Perhaps I should open my own coffee shop when I retire. What would I call it?
I will add captions as I have time this weekend . . .
PhyFl18–SS3.2.1 Packet 3 Tree stamps with class!
PhyFl18–SS3.2.2 the perfect gift
PhyFl18–SS3.2.3 Monday 12/3/18
PhyFl18–SS3.4 Prob 3.5.1c
PhyFl18–SS3.2.5 Problem 3.5.1e
PhyFl18–SS3.2.6 We were SO close to the actual number. The best in 30 years! 30 years I tell you! Are these the glory days of NHS Physics?
PhyFl18–SS3.2.7 Orange to Blue.
PhyFl18–SS3.2.8 Prob 3.5.2
PhyFl18–SS3.2.9 the triop graph of 3.5.2
PhyFl18–SS3.10 Tuesday 12/4/18
PhyFl18–SS3.2.11 Basketball (550g) vs. tennis ball (55 grams) Despite 10X the mass, the basketball falls at the same acceleration as the tennis ball.
PhyFl18–SS3.2.12 So why do they fall at the same rate?
PhyFl18–SS3.2.13 THe answer is: Inertia vs. force. Inertia is NOT force. It is a property of matter as Bill Nye says, but it is so much more. I’ve always thought that was a stupid thing to repeat over and over. Yes it is a property of matter, big deal. It is a measure of the RESISTANCE to change in velocity that na object has. The more the resistance the more the mass.
PhyFl18–SS3.2.14 Mass is the measure of the resistance
PhyFl18–SS3.2.15 So then why does the Big ball fall at the same increasing speed as the small ball so that they hit the ground at the exact same time with the exact same speed? The answer is that the Big ball has 10X the resistance to fall than the small ball. Gravity puts 10X the force on it to get it to fall. The tennis ball has 10X LESS force pulling on it, but it only offers 1/10 of the resistance. It’s a perfect balance between force of the Earth’s gravitational pull and the relative resistance each object offers.
PhyFl18–SS3.2.16 10X the force, 10X the resistance
PhyFl18–SS3.2.17 . . .
PhyFl18–SS3.2.18 One of the hours discussed the effect of air drag. We will look at this more second semester. This is me trying to give a quick and dirty explanation of air drag. Will not be on the next test.
PhyFl18–SS3.2.19 The offical Newton’s 1st Law of Inertia. We are trying to get this down to 4 words so we can put it on a t-shirt.
PhyFl18–SS3.2.20 Wednesday 12/5/18
PhyFl18–SS3.2.21 Prob 3.5.3
PhyFl18–SS3.2.23 Prob 3.5.6
PhyFl18–SS3.2.24 Prob 3.5.6b
PhyFl18–SS3.2.25 Prob 3.5.6 birth of the first green
PhyFl18–SS3.2.26 Prob 3.5.6 The easy version of the 2nd Green Launch Equation
PhyFl18–SS3.2.27. How the velocity vector changes as an object falls.
PhyFl18–SS3.2.28 Thursday 12/6/18
PhyFl18–SS3.2.30 1st Green Launch Equation
PhyFl18–SS3.2.31 2nd Green Launch Equation
PhyFl18–SS3.2.32 Negative Free Fall Trios
PhyFl18–SS3.2..33 We talked about the St. Louis Arch because I thought at one time that it was a negative parabola. Turns out it is much more complicated.
S3.1.2 From our hallway circular – SHM motion exercise
S3.1.3 Hallway positions
S3.1.4 Circular vs. Simple Harmonic Motion (SHM)
S3.1.5 last question on sheet 3.2 A sort of new equation involving period (Tp) and omega
S3.1.7 A vector has a head and a tail. Isn’t it cute?
S3.1.8 We are going to study the gravity force vector a lot.
S3.1.9 Here is an example of the use of force vectors.
S3.1.10 Weird things happen when you add up arrows.
S3.1.11 3 + 4 = 7 maybe . . . 3 + 4 could also equal 5. It all depends on the angle between the vectors.
S3.1.12 Here 3 + 4 = 6.
S3.1.13 Here 3 + 4 = 2
S3.1.15 Here 2 + 3 + 4 = 1
S3.1.16 Here 2 + 3 + 4 + 5 = 1
S3.1.18 There are two ways to describe a vector. Here is the proper description of a MAP VIEW.
S3.1.1 9 Here is the proper and description and it also shows the component description.
S3.1.20 THis is the proper description of a PROFILE VIEW.
S3.1.21 I think this one is from the front of sheet 3.3
S3.1.22 This is from the front of Sheet 3.3
S3.1.23 We will always take the acute angle. At least until April when we start talking about work and energy.
S3.1.25 some examples of vectors we use.
S3.1.26 Know your vectors and scalars
S3.1.27 Believe it or not, you CAN represent surface area of a sphere with a vector. In fact, Gausses Law (in Electromagnetics) depends on it. BUT . . . you CAN’T Represent volume with a vector since volume is omnidirectional. If we lived in 4 dimensional space, then you maybe COULD represent volume with a vector.
S3.1.28 You really should watch a couple of videos with Sean Carroll (Cal Tech Physicist) He even has a Podcast you might enjoy. The JRE’s with Carroll are great.
S3.1.29 Time is like a river. There can be small eddy currents where it goes backwards for a nanosecond or two.
S3.1.30 . . .
S3.1.31 Here is Levi’s brilliant interpretation of the progression of time . . . and the second law of thermodynamics.
S3.1.32 If there is a big crunch the arrow of time will be flipped and time will go backwards. 2nd Law of Thermodynamics will no longer be valid. The thing is, this probably will NOT happen. The universe will likely end in a “heat death” where Dark Energy finally gets its way and everything is separated. Even your quarks. Yea!!
S3.1.34 From the Guest Speaker. Email her for a possible $5000 scholarship.
S3.1.35 Field trips are the best part of Geology/Geophysics
S3.1.36 SO we spend most of Thursday at the stadium studying the effects of the gravity vector.
S3.1.37 1st hour
S3.1.38 2nd hour
S3.1.39 3rd hour
S3.1.40 6th hour
S3.1.41 7th hour. Who’s that old dude? Oh yeah, DeeLee of course!
S3.1.42 1st hour’s free fall data
S3.1.43 2nd hour’s free fall data
S3.1.44 3rd hour’s free fall data
S3.1.45 6th hour’s free fall data
S3.1.46 7th hour’s free fall data
S3.1.48 Here are all the class average free fall times. The overall average for the little ball was 1.42 seconds. The big ball’s average time was 1.55 sec. The two times should have been the same since all objects fall at the same acceleration. It comes down to reaction time.
S3.1.49 The percent difference needs to be with 10% in high school to be considered negligible (kind of depends on the experiment). The two times should have been the same, but there is an excuse here, mainly . . . air drag is different on each ball, but my guess is the main culprit was your reaction time.
S3.1.50 There are A LOT of rules for siggies. I will leave it up Mr. Powell to torture you with those if you take AP Chemistry. We will just go with determining the number of siggies you get from measured values. The first iffy is the last siggy.
S3.1.51 We had 3 siggies in our ∆y. Whatever digit is the iffy one (the ± one) that is the last siggy. So, three siggies for the height. Three siggies is plenty for high school work. The problem is, how many siggies can wee get out of the time?
S3.1.52 So remember that our goal was to determine what the acceleration of the balls were due to the gravity force vector. Here is the kinematic equation we will use to determine that acceleration
S3.1.53 Our over all average time (after over 200 free fall drops) was 1.5 seconds (that’s to two sigs) Time limited us to two sigs. We had three sigs with the height, but that extra sig fig was wasted since the time only had two siggies.
S3.1.54 Here is a new formula for you. Percent Error is the moment of truth. It tells you how close you are to the accepted values. In this case, the accepted value for acceleration due to earth’s gravity. To two sigs it is 9.8 m/s/s. Our value (when all times from all classes are averaged) is 9.9 m/s/s. That is a ONE PERCENT ERROR. That is the closest that we have come in 30 years. A little luck? maybe. A lot of skill? . . CERTAINLY!
S3.1.55 Monday we will quantify the human reaction time.
I will keep adding captions throughout today (11/17):
PhyFl18-SS2.6.1 A new record? I can’t see that small to count. We have one more of these Astronomy talks. You all have impressed them so much that now they want to do more talks about all kinds of science subjects. Also, the Biology Department wants you to come to their lectures. You have power in your numbers. Everyone at OU wants a piece of the NHS Physics crowd.
PhyFl18-SS2.6.2 this is left over from Test 2A, but it was the most missed problem. secant slopes make the steps and tangent slopes make the dots in the middle each step.
PhyFl18-SS2.6.3 It is where the famous equation for average velocity comes from. the v bar is the slope of the secant line, the Vo is the slope of the tangent line at the beginning of the segment and the Vf is the slope of the tangent line at the end of the segment. This only works for Trios.
PhyFl18-SS2.6.4 Here is a few more graphs of a bullet in a barrel. Notice how the acceleration is front loaded because explosions are P-waves (pulse or pressure) Sometimes called a concussion wave. This also shows the rifling (spiraling) of the bullet.
PhyFl18-SS2.6.5 The blue rectangular area from the AVERAGE acceleration is the same as the the area under the actual instantaneous acceleration. Both, in this case, are 600m/s
PhyFl18-SS2.6.6 Is this a Crackle? (a sextet) or maybe even a pop (septet) We would have to break down the function of the front loaded mountain to find out.
PhyFl18-SS2.6.7 Okay, so here is one like THT2B.18. Even though we know it is just the AVERAGE acceleration we can use that area to determine the velocity of the bullet as it moves through the barrel and we can even determine the length of the barrel. It is simply a matter of finding the areas of the lower graphs to determine the function of the graph above. This is the basis of integral calculus.
PhyFl18-SS2.6.8 Another example
PhyFl18-SS2.6.9 this one is similar to the take home test 2B
PhyFl18-SS2.6.10 you should try it yourself. try to go from an a vs. t graph to a v vs. t graph and then to a x vs. t graph.
PhyFl18-SS2.6.11 Here is a tough problem. I would look it over REALLY good before the test Monday.
PhyFl18-SS2.6.15 2.14.5 Asteroid coming to earth. I am in the process of writing one like this for the test 2B. Just a heads up.
PhyFl18-SS2.6.19 part of 2.14.6
PhyFl18-SS2.6.22 Be careful when you fill in the boxes on the front of your packet organizer. NO FALSE CHECKS!
Here are the important screenshots from last week:
PhyFl18-2.5.1 Chuck with my childhood dream girl
PhyFl18-2.5.1A Here is a good example of how to do board work using Deipa
PhyFl18-2.5.1B Another good example
PhyFl18-2.5.5 I the speed of light is about a million times faster than the speed of sound. That is why you see the lightning and then hear the thunder 5 seconds later if the lightning was a mile away. (since speed of sound is about 1100 ft/sec which is about a mile every 5 seconds. Still, that’s pretty daggone fast. I wish I could go a mile in 5 seconds. That would give me a lot more time at home at lunch. Just sayin.
PhyFl18-2.5.7 3rd Orange Equation derived part 1
PhyFl18-2.5.7B 3rd Orange equation derived — part 2.
PhyFl18-2.5.8 So let’s talk guns and bullets.
PhyFl18-2.5.9 What is the acceleration of the bullet in the barrel of a gun?
PhyFl18-2.5.10 2.12.5b How long does the bullet stay in the barrel?
PhyFl18-2.5.12 2.12.10a the physics part is not bad
PhyFl18-2.5.13 weird units, but we can’t have double decker fractions in our unit analysis.
PhyFl18-2.5.14 2.12.10a. Easiest way to work this difficult problem.
PhyFl18-2.5.17 Back of the Envelope Demo of a ball rolling up and down the ramp. How to determine the hidden acceleration
PhyFl18-2.5.18 2nd hour’s BOE
PhyFl18-2.5.19 3rd Hours BOE
PhyFl18-2.5.20 6th hours BOE
PhyFl18-2.5.21 7th hours BOE
PhyFl18-2.5.22 Ball up and down ramp in general
PhyFl18-2.5.23 Perfect bow tie. Positive right triangle represents the ball rolling up the ramp, brown right (negative) right triangle represents the ball rolling down the ramp.
PhyFl18-2.5.25 handgun bullets vs. rifle bullets.
PhyFl18-2.5.26 bullet stuff
PhyFl18-2.5.27 bullet stuff
PhyFl18-2.5.28 bullet stuff
PhyFl18-2.5.29Rifling the inside barrel of a gun made the bullet come out spinning which made it much more accurate. Sort of like a spiralling football throws much more accurtately than a knuckle ball football.
PhyFl18-2.5.30 Average acceleration of the bullet in the barrel. THis is a gross approximation. We spent most of the hour talking about why it was wrong. We HAD to assume it was flat or we couldn’t have attackjed the problem with the Orange Trio Equations
PhyFl18-2.5.31 The acceleration is zero when the contained explosion first occures and the horizontal acceleration of the bullet is zero when the bullet leaves the barrel since there is no more pressurized expanding gas pushing it through the chamber. so the parabolic shape is better than a flat a vs. t, but it is still wrong. The reason involves p waves.
PhyFl18-2.5.32 Even though the average acceleration vs. time is a gross approximation of the true instantaneous acceleration, we can still use the approximation to accurately determine the final velocity AND the length of the barrel. Wow, this Physics stuff is pretty cool. Knowing a little bit about the acceleration of a bullet in a barrel tells me how long the barrel is. Magic? Nope, physics with a little calculus.
PhyFl18-2.5.33Kinetic theory needs to be brought up to start to understand why the a vs. t graph is not parabolic in shape. Basically, Kinetic THeory says that everything is made os molecules (this idea is only a little over 100 years old). Phillip Leonard was a jerk and turned out to be a Nazi, but he WAS right about molecules. Einstein believed him, but he hated Einstein because he was a Jew. Can you believe that? That is like thinking someone is less than you because of the color of their skin. What kind of a monster would ever believe that? Anyway . . . the air molecules in this room are moving about 800-900 mph. You like that because it makes your skin vibrate at just the right frequency. Ahhhh. . . warmth.
PhyFl18-2.5.34 So molecules (and therefore everything) has three possible types of motion.
PhyFl18-2.5.35 There are different types of waves. We are talking about pulse waves today, but there are Shear waves, Raleigh Waves, Love waves. Most waves we deal with in Physics (like sound waves) are P waves. The P stands for Pulse or Pressure)
PhyFl18-2.5.36 . . . .
PhyFl18-2.5.37 Sounds that reach your ear originated with a manipulation of the air molecules by the p waves eminating from the source. It still blows me away how air molecules are so quickly rearranged into areas of compression and areas of rarefaction. We can measure this with an oscilloscope.
PhyFl18-2.5.38 SOme classes have n’t gotten to this yet, but this is the upshot of the p wave inside the barrel of the rifle. It makes the graph of a vs.t front loaded.