Askey Physics

All things Physicsy

11/5-11/9/18 (Orange Kinematics)

Posted on November 10, 2018 by daskey

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

: PhyFl18-2.5.2 MONDAY

: PhyFl18-2.5.3 2.12.1

: PhyFl18-2.5.4 2.12.4

: 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.

: PhyFl18-2.5.6 TUESDAY

: 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?

: PhyFl18-2.5.11 WEDNESDAY

: 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.

: PhyFl18-2.5.15 2.12.10b

: PhyFl18-2.5.16 THURSDAY

: 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.

: PhyFl18-2.5.24 FRIDAY

: 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.

: PhyFl18-2.5.39 more about this on Monday.

%d bloggers like this: