Jump to content

BrandyBoy72

Members
  • Content count

    21
  • Joined

  • Last visited

Community Reputation

1 Neutral

About BrandyBoy72

  • Rank
    Member
  1. Quantum Leap

    your chemistry class sounds cool
  2. The Weight of Air (and birds)

    Commonly pondered question: How much does all the air on the Earth weigh? Make your predictions now: a) more than the Earth itself 0 kg, air weighs nothing, duh c) More than all the birds on Earth d) 7.89 kg One cubic meter (1000 liters) of air weighs 1.292 kg (so if you chose d you are probably already wrong) But that doesn't help us much, because as you go further up in the atmosphere, the density changes. The mass of the air is the same, but there is just less of it per cubic meter. Calculations: Another way to approach this problem: the air pressure at sea level is 14.7 psi, in other words, all the air in a 1in x 1in area all the way up to the top of the atmosphere would weigh 14.7 lbs ***we'll convert to more physics like units later*** Now we need to find out the surface area of the Earth: Earth's radius: 2.5E8 in (again we'll convert later) Surface area of a sphere: A = 4*pi*r2 = 7.854E17 in2 Now multiply: 7.854E17 in2 x 14.7 lbs/in2 = 1.155E19 lbs All the air in the Earth's atmosphere weighs approximately: 5.3E14 kg Compared to: All the birds on the Earth: net weight(very approximately) = 3.6E12 kg (if you chose c at the beginning, you win *suggest prizes in the comments*) The Empire State Building(approximately) = 3.3E8 kg 500 really big boulders(exactly) = 3.4E4 kg
  3. Units and Vector Directions

    In my previous post, I realize that I gave an incorrect answer to the solved problem. Not so much as incorrect, the number sure is right, but it is a vector (has magnitude and direction) and I treated it like a scalar (magnitude only), by leaving out direction. The answer should have been a=2.254 m/s2 downwards. Another thing I left out in the original answer was units, something that it is common for me to neglect or often mess up. Any time I am read a word problem for the first time I do what I was taught, take out only the useful information, ie. the numbers. And not uncommonly these numbers are connected to units, which I will inconveniently ignore. And by the time I get to the end of the problem, I will probably have an answer that is off by some power because I have not converted grams to kilograms or something like that. So remember: always use correct units and label directions on vectors!
  4. Elevators are Evil

    A friend of mine in AP physics 1 needed help on a web assign question in which a man's weight changed by .77 times after the elevator he was on started to accelerate. I explained to him how I would set up a system of equations where mg=weight(w) and the weight afterwards .77w=m(g+aelevator). And then set them equal: .77mg=m(g+a). m's cancel and then you solve for a getting a=2.254. A throw back to the test with that one SRQ with the guy pulling on the elevator, shows us that elevator problems plague physics students everywhere. But it also shows us that we are learning and we have at least made some progress in our physics careers.
  5. The Physics Behind Fidget Spinners

    I dabbled in fidget spinners once, it did not go well. Loved the Dude Perfect video!
  6. Musical Chords: C and C# vs. C and G

    The first video sounded so cool, I loved listening to that first sound with c and c#. But RIP headphone users on the second video lol
  7. Archer's Paradox

    Archery is pretty intense when you think about it with physics on the mind. There's tension in the string, aerodynamics (arrow dynamics), kinematics, oscillation, and probably a whole lot more things too. In archery there is this thing known as the "Archer's Paradox" which has to do with the oscillation of the arrow during it's flight. As an arrow flies through the air, because of the flexibility of the arrow shaft, there is an oscillation that occurs. If the arrow were not flexible, if it were rigid, then it would not fly in the direction it is aimed. You can imagine that the arrow is bending around the bow as it is shot. This oscillation changes based on the flexibility of the arrow and the strength of the bow.
  8. Infinity Miles per Hour

    Can you travel at infinity miles per hour? Well, infinity isn't really a number so, probably not. But how fast could, we'll say a person, travel? I would say the speed of light is the fastest possibility, but let's start out a bit more realistic. Usain Bolt can run at 28 mph, but this is physics, so 12.5 m/s. Not a bad start. How about something faster, the fastest train is the Maglev, at 120 m/s. The fastest land vehicle - Thrust SSC at 341 m/s. The fastest speed by a manned vehicle was the Apollo 10 at 11082 m/s, but that's still only about 0.0037% the speed of light. But wait, we're on the Earth, aren't we, and that's moving fast, about 30000 m/s. And now that we've considered that, how fast is the milky way galaxy moving? 581152 m/s! That's 0.19% the speed of light. I don't think that it is reasonable that people will get close to traveling faster than our galaxy, at least any time soon, so guess it's time to give up. But, let's consider something, could we already be traveling at the speed of light? Here's the idea: there is a person at point A standing still, and a car moving at 16 m/s, and there is a point in the car, point B, where relative to that point, the car is not moving (kind of like how relative to us, the Earth is not moving, but relative to the Sun, it is moving quite fast). So, from that point B in the car (if you can imagine) the person standing at point A is moving, relative to you being still, at 16 m/s. So, considering this example of relativity, can we say that relative to a photon, we are moving at the speed of light? Yes. Wait! No, no, no that can't be, we did not consider something, I said there was a relative point B where the car was not moving, so there would have to be a point where, relatively, a photon is standing still, and that is not possible in any reference frame. (Also technically there is no reference frame where anything but a photon can be moving at the speed of light) - but we still went through with this thought procedure in light of that... get it?
  9. Physics in Ap Chem

    I prefer potential energy over kinetic energy
  10. A Haunted Blog Post

    c) 15.5 N/yr
  11. Pokeball vs Pokemon

    If a pokeball doesn't work, just use a masterball
  12. Linear* Momentum of the Earth

    P=MV Momentum of the Earth (Linear): Mass of the Earth: 5.972*10^24 kg ; the weight of the Earth is measured using the equation FG=(Gm1m2)/r2 taking an object that has mass and finding the force that the Earth exerts on it. Velocity of the Earth: 30000 m/s ; We find the velocity of the Earth by knowing that the Earth travels around the Sun in one year, now we only have to find how far it travels. We have to find the length of its ellipse around the sun, which is approximately a circle (or close enough - this is physics after all where 9.8=10...) So we have to find the radius which is the average distance from the Sun to the Earth which is known as an Astronomical Unit (AU) which is 149,600,000 km. So C=2*pi*r2 ; C=2*pi*(149,600,000,000m)2 and divide that by one year to get the velocity. Now multiply mass and velocity together to get momentum: 5.972*10^24kg * 30000m = 1.7916*10^29 N*S - pretty big
  13. Losing Weight Can Save Lives

    I never fully understood what the constant "b" was, does it relate to surface area? That's what I always thought
  14. Physics APC or ATC?

    Recently I went to an indoor climbing facility downtown, called Rock Ventures. I love rock climbing, there's a thrill in all that built up gravitational potential energy. However, it is completely safe thanks to our friend the pulley. There are multiple types of rock climbing, indoor climbing, free climbing, and solo climbing. Solo climbing has no ropes involved whatsoever, just a person on a cliff. Free climbers use ropes, but only to prevent from injury in segments, not to assist in the climb. Indoor or sport climbing is what I was doing, this type involves a pulley system. The interesting part of this system, not really having to do with pulleys, is the ATC that is used when belaying (yes it stands for Air Traffic Controller, you'll soon see why) The ATC is used by the belayer, a person on the ground spotting the climber, to control their ascent and descent and how much slack is in the rope. The ATC is a device which the rope goes through to be manipulated by the belayer. There is a lead rope and a slack rope, when they are parallel, the rope is free to slide - in this position the belayer can pull excess rope through as the climber ascends, getting rid of slack makes the climb safer in case the climber would fall. When the slack part of the rope is pulled down towards the ground, there is a frictional force between the ATC and the rope, which under even a large amount of tension, would not allow the rope to slide. The ATC is a very simple, yet genius device that makes it possible to safely climb for fun, and for that, I thank physics
  15. Loafin' Around

    This isn't passive aggressive in any way is it? Don't worry, things will get done when they need to be, don't think too much about it

Terms of Use

The pages of APlusPhysics.com, Physics in Action podcasts, and other online media at this site are made available as a service to physics students, instructors, and others. Their use is encouraged and is free of charge. Teachers who wish to use materials either in a classroom demonstration format or as part of an interactive activity/lesson are granted permission (and encouraged) to do so. Linking to information on this site is allowed and encouraged, but content from APlusPhysics may not be made available elsewhere on the Internet without the author's written permission.

Copyright Notice

APlusPhysics.com, Silly Beagle Productions and Physics In Action materials are copyright protected and the author restricts their use to online usage through a live internet connection. Any downloading of files to other storage devices (hard drives, web servers, school servers, CDs, etc.) with the exception of Physics In Action podcast episodes is prohibited. The use of images, text and animations in other projects (including non-profit endeavors) is also prohibited. Requests for permission to use such material on other projects may be submitted in writing to info@aplusphysics.com. Licensing of the content of APlusPhysics.com for other uses may be considered in the future.

×