willorn

My instinct tells me there wouldnt be significant weather changes from widespread use of wind turbines, but the kinetic energy of the particles in the wind has to go somewhere. Are you prompting that there would be slower windspeeds if turbines were stationed worldwide?

Just about halfway down the page that moe.ron shared on his blog is a cartoon that got me thinking. If a person had a stick one light year long (or more), and this person pushed the stick, would the kinetic energy reach the end of the stick faster than light if photons were released at the exact same moment? I'm thinking that the kinetic energy in the push would be just another energy wave moving through the particles of the stick, so I believe that the light would reach the end of the stick first, even if it would be years later. Of course I'm hoping that someone else has a thought about the matter. [ATTACH=CONFIG]80[/ATTACH]

unintentional my physics fanny

I was attempting to recreate the situation on a real basketball but using a longer object on top (I didn't have a hockey puck), and it does indeed look as though the long object leaves the basketball before getting halfway down. I am beginning to think that this is because the fulcrum location on the puck changes as it moves down the basketball until the force of gravity on the puck causes it to rotate until it leaves the basketball (because it is orientated more vertically at this point).

I have limited knowledge of the normal force, as I learned in physics B that it is simply a "reactionary force" always with equal magnitude to the initiating force unless deformation occurred. In physics C we spent perhaps 5 minutes learning that the normal force is a summation of resistance forces from everything that the initial force is "pushing on." With that in mind, the normal force is the only force in play that I imagine would be able to cause the puck to leave the basketball early. BUT I assume because there is no deformation to the basketball or the puck that the normal force can be no more than equal to the weight of the puck at any time, and so there is no acceleration outward. Please disprove my statement.

Kicking won't solve your problem

This may be the simplest device ever created with the weirdest laws of kinematics surrounding it. What is it? Well, its a funny looking loop that flies up to 655 feet. This thing has broken world records. Thats over 6 football fields by the way. But what are the laws of physics surrounding this thing?? http://www.x-zylo.com/index.php?option=com_content&view=section&layout=blog&id=5&Itemid=38 I wish I had definitive answers. Just be observing the way that it flies, I can see that it moves like a frisbee that is thrown forward, and since a frisbee operates by creating a low pressure zone on top of itself so that it gets lift, I can only assume that this toy is magically creating a low pressure zone in front of itself…any input on this topic would really help me get a weight off my shoulders. This means you physics C!

I've been having serious difficulty completing all sorts of physics problems lately, and I felt that maybe I wasn't understanding the basic principles of SHM and gravitational forces etc. So naturally I turned to good 'ol Walter. But I found that instead of listening to his lectures, I was often just waiting to watch him draw a dotted line on the blackboard. So I had to re-watch a number of lectures and I was wasting a bit of time. So I turned to the other great lecture-er who some of you may not be aware of "Richard Feynman." His lectures on our current material are a bit harder to find hosted anywhere for free, so I currently own a set of Feynman lectures on CD. Its been a tremendous help to me, and although it was a bit expensive I think everyone ought to know about Feynman. P.S. Does anyone know how many blog-posts we should have up by this time? I know I'm behind at least one.

I'm definitely with you on this one. Physics partys are awesome.

Maybe I'm forgetting something critical, but what force is acting on the puck such that it accelerates outward as well? The Normal force on the basketball to the puck couldn't be unbalanced I figure, so I'm left wondering what is unaccounted for.

Pre-Disclaimer: Please do not watch the attached video if you can't stand to watch blood being drawn. But by all means if you can stomach it, take this disclaimer as encouragement to continue reading. Don't hold your breath on this one. It's very literally a video of someone giving himself a papercut in slow motion. (helpful hint: skip to 1:25) so how does the paper "molecular knife" muster the force to cut the skin? Like the video mentioned, it has to do with pressure exerted. Its a principle of physics that pressure is the force per unit of area that is acting perpendicular to the surface in question. We know that even though skin is weak, its difficult to apply force with your hand such that your skin breaks under the pressure. So, the incredibly small surface area of sideways paper being applied perpendicular to the skin is enough to "part the molecular sea." Post-Disclaimer: In no way does this blog endorse self-mutilation of any kind. even if it does make you feel like micro-physics molecular moses.

It would seem so. What you have to keep in mind Newton's Second Law of Physics F=ma. A force results only in an acceleration. AND we know that if an object has Fnet=0 (that means that there is either no forces acting on an object, or that the forces acting on the object cancel each other, as in this case) then the object is not accelerating in any direction. There are only two possibilities for an object that is experiencing no accelerations; this comes from Newton's First Law: an object will remain at rest or in constant motion unless acted upon by an outside force. Your object, however, also has a velocity. Ergo, your object is moving with constant velocity. Hope this helps!

Probably the craziest proof to date! awesome. I wonder if there's a way to explore the concept without the Matrix perspective?

Very very cool. I tried it for myself.

Haven't you ever wondered why when a dog drinks water from a low bowl, its much messier than when a cat drinks from that same bowl? Of course you haven't. But you're wondering now! So here's the physics explanation and a few accompanying videos. The Answer: There's really not too much difference. Both the cat and the dog utilize the principal of water/liquid displacement in order to get the water to their mouths. The displaced water is then trapped in the "backwards spoon" that both animals create with their tongues. The difference between sloppy dog and cleaner cat is that the cat aims straight down (perpendicular) and uses less force to displace less water per drink while the dog uses more force to drink more water in less time. The dog also angles its head when drinking, and some water spills from the "backward spoon" as a result of earth's gravitational field imparting a force on the system. The most important difference is the force the dog uses to displace the water. The kinetic energy of the dog's tongue creates a wave in the water that sloshes all the way to the edge of a small bowl. When the crest of the wave reaches the bowl's edge: wet floor. The cat? There's just not enough force in the cat's drinking to create a wave to crest over the lip of the bowl. Remember, water molecules tend to hold their overall shape, so if at all possible, the water will fight to stay in the bowl. I wondered if a cat the size of a greyhound would be just as sloppy as any dog, so I looked up the following video. http://video.google.com/videoplay?docid=-7267401144989927060# As you can see, this cat too drinks very neatly. But again, its simply because the cat uses less force to displace water with its tongue. Is drinking style an evolutionary trait? who knows, I'm just a physics student.

I would say right away that the density of water has everything to do with it. My common sense is telling me that a denser object would accelerate faster, but of course I'll go look this up. It may also have to do with the fact that water is transparent and snowflakes are opaque. (to relate this fact to physics, we can say that snow reflects photons back to our eyes, while water reflects fewer of these light particles/waves back into our retina). Try tracking a single falling water droplet with your eye sometime; with the right backdrop, its not as hard as you may initially think, at least if you start with your eyes straight ahead. It should be noted however, that in pouring rain the hydrogen bonding dipole forces that occur naturally in water will cause many, many water droplets to merge with each other during their flight, making things much more difficult. And yes, I tracked water droplets for fun as a kid.

If you weren't a super duper physics student, it would seem so! However, Forces cause accelerations on an object. and if an object is not accelerating in any direction, two things can be happening to the object. It can either be motionless OR in constant motion; talk to yourself about the definition of constant velocity, thats how I wrapped my brain around that one. Velocity only changes with acceleration (forces), so a constant velocity means no forces or forces that cancel each other out. I hope this helps!

Thanks so much

I would absolutely love to do that experiment and a physics podcast! I'm 100% on board. As for the Nitrogen: SWEET

Could it be that a follow through just ensures the player doesn't anticipate the close and pull up, decreasing force on the ball?

Very Impressive!! Would love to know how you got fancy equations into your blog

These past few days of physics have been some of the most interesting of my fledgling career. Between greek letters that make my math look difficult and a crash course in Integrals, things are looking collegiate. Of course, its also been some of the most challenging physics I have done. What really excites me about the class recently is that rote memorization alone won't give me the ability to solve rotational problems. Finding a good substitute for dm often takes a certain kind of thinking that really makes me feel as if I'm cut out for the field. Personally, I feel that I'm really doing physics problems now. On another note, I figured I'd share a certain youtube video featuring a tiny experiment in superconductivity. This video (and concept) is one of my favorite concepts in physics. The video also serves as a great way to illustrate the abstract concept of Magnetism and Magnetic Fields. You can see as the student moves the upper magnet about the lower one, the magnet slants to the side. This is because a magnetic field has a real and physical shape, and exerts a force according to that shape. When the student coated both magnets in liquid nitrogen, he change the shape of the field. The result is that the upper magnet rests on the field at an angle, because the field is at an angle. Its something you don't always think about. For those of you who are critical of my interest in superconductivity, check this link out. Or just read it because you like to read about advances in physics. http://www.sciencedaily.com/releases/2006/03/060307084618.htm

Graphics should be working now

could it be that the change in time for the impulse is made considerable longer by the deformation of the trampoline and then force that results in the upward direction is much less than it otherwise would have been?

Since there's nothing better than rolling spheres and sliding blocks in physics, I figured my first blog post ought to be about one or both of the two. Unfortunately, I can't think of anything with sliding blocks that hasn't already been done, so this post will be about spheres. The Question I'm trying to answer will be: "If we are supplied with given information about a billiards player's first shot in the game (the "Break") can we determine the resulting force on the two corner billiards balls using momentum and impulse? Assuming that the Triangle Rack is set up perfectly. Let's just say that the average pool shark can imbue his 160 gram cue ball with 20 Newtons of Force in .05 seconds. Billiard Balls are made of Phenolic Resin Plastic, which has a notoriously low coefficient of friction. Take into account the soft cloth table, and the fact that the slipperiest solid we know of has a coefficient of .02, and we can reasonably assume that the coefficient of friction between the balls and the table could be .15 If the cue ball is to be placed 1 meters from the leading billiard ball as shown below. [ATTACH=CONFIG]60[/ATTACH] We can than calculate the velocity the cue ball will have the moment before it contacts the set of billiard balls using common Kinematics equations. [ATTACH=CONFIG]58[/ATTACH] The Circled Value is the velocity of the cue ball just before it hits the first billiard ball, taking deceleration of friction into account. In this case, the Cue Ball has an instantaneous velocity of 6.005 m/s which we can safely round to 6 m/s. Therefore, because p=mv (where p is rho/momentum), the cue ball strikes the others with .96 N*s. Therefore, based on our laws of conservation of momentum, we can determine that (since our billiard balls are all perfectly and symmetrically arranged and touching) that the momentum from the cue ball is transfered to the corner balls completely. The fact that our billiard balls are all in contact is important, because any distance between them would be closed by the impulse from the cue ball and a loss of energy (momentum as well) would be lost. [ATTACH=CONFIG]59[/ATTACH] In the above snapshot, we can see that the momentum of the cue ball just before impact is equal to half of the momentum given to the corner balls. Realistically, the corner balls would receive momentum roughly equivalent to M/2 because for each billiard ball that receives the momentum of the cue ball (imagine the total energy passing through each ball along the outer edges) some of that ball's momentum is transfered to the two balls in front of it, but not equivalently. Another graphic can explain this phenomena. In the graphic, the ROYGBIV scale denotes--roughly--the vector magnitude, with Red being the greatest. Notice that the black circle indicates a close-up vector addition analysis that betrays how initially, a billiard ball may look as though it doesn't have a trajectory that lines up with the pocket, but that a normal force does indeed cause the ball to be propelled towards the corner pocket (but only of course if you are a billiards master and can hit the cue ball dead-on)! Regardless, the setup of the game is such that the corner balls receive the most of the original momentum and are propelled towards the corner pockets. For this reason the corner balls are the billiard balls most commonly sunk by the break. In fact, a billiards player would be foolish not to take advantage of this setup on his break, physics says so Back to math. The law of conservation of momentum (Mi=Mf) dictates that the momentum of the cue ball must equal the sum of all resulting momentum. Remember, in reality there are other momentum for each ball, but the majority of momentum goes to the corner billiard balls. Mi=Mf => mvi=(mv)+(mv) => (mvi)=2mv => (mvi)/2m=vi/2=v Therefore, if you apply a reasonable 20N force to a regulation 160 gram cue ball and you are GOD when it comes to aiming your cue ball for the break, you can expect each corner ball to shoot off with approximate velocity 6/2= 3m/s toward the corner pocket. :einstein)