Centripetal Force and Flying Stuff

Journal 7: Ok so, evidently blogger doesn't like my photos and won't upload them...that's a problem.  Sooo, anyways, last night my dad and his friends had their annual Family Christmas Party and it was hosted at our house this year.  It's tons of fun, since they've been friends since highschool and such, they decided to have these get together parties, full of games, gifts, and food.  While the adults were down stairs, the kids were upstairs playing around and one of them began swinging one of those squishy balls with the the squishy string attached to it, almost like a sticky hand.  Then, while whirling it around, it flew out of his hand, and flew tangent to the point of where it was released.  This reminded me of the example Mr. Kohara used in class with the tennis ball and the string, and how he always yelled "I saw that, TANGENT!" whenever someone dropped the pink ball from the loop toy, our class to dextrously played with (not).  From this example I saw centripetal force in action as the circular path the ball made and its distance from the center (the boy's finger) was the radius, and how fast it was going was its speed.  Yeah, its pretty simple, nothing too awe inspiring here.

Journal 6: Momentum is Masked.  Momentum can be found everywhere around us as most of physics can. This principle/ concept of physics is a vector quantity of motion as is defined as an object's mass times its velocity and is represent by the small letter p.  Thus the equation for momentum stands as p=mv, its units in kilgram times mass divided by time; kgm/s.  This concept can be found in moving cars, pool balls, actually generally anything moving.  Now, although seen with the example of the clicky-clack balls as Mr.Kohara stated this automatically reminded me of them.  My brother created this bola to throw and trap my brother in, though it is too small to do its intended purpose.  So when he threw it at me I easily caught it at the black handle and I saw the green and red ball hit each other and the clicky-clack balls came to mind.  Now these balls just as this bola exhibit the law of conservation of momentum, basically none of the momentum is lost.  In a real clicky-clack ball set up, the metal balls would continue swinging for quite awhile, however, the balls in the bola would swing for only less of the time.  Although the green ball may look bigger I confirmed with my brother he used the same amount of clay, just that the green one was smashed a little bit.  In this example, kinetic energy is also conserved and the energy remains constant throughout the system.  So the clicky-clack balls and the bola are basically the same physics example of momentum hiding where you would least expect it. -Seriously anyone know how to get the pictures up? Blogger continues to show the "uploading images" screen and I've waited fifteen minutes...-

Work and the Wonderful World of Physics

Currently, in Physics we are learning about potential energy, kinetic energy, and work.  In this simple example of lifting a calculator, we can see work and energy in action. Anybody recognize which problem on the weekend's homework it is?  As I exert force on the calculator and move it in the direction that the force is exerted, I am doing work.  This definition shows that by simply holding an object in place, no work is being performed.  The force I exert is in an upward motion and is the same for the direction the force is pushed in.  This is kinetic energy in effect or the energy of something in motion.  This also exhibits potential energy or the energy an object has relative to the a set point when not moving.  If we set the ground as our reference point of zero, and for this example say I am exerting 10 joules of kinetic energy in my work.  This 10 joules will later transfer to all potential energy when I hold the calculator in place above my head.  There will be no kinetic energy at this point, as there is no movement.  In relation to the ground, if I hold the calculator above my head without moving it there will only be potential energy.  Likewise, if i set the calculator on the ground and move it horizontally there will only be kinetic energy.  However, any combination of horizontal and vertical movement will result in the object having potential energy (PE) and kinetic energy (KE).  Kinetic energy for those of you who have for some mysterious reason have not realized it yet relate to kinematics thus movement.  Potential energy is the "potential" for the object to move.  Through these mundane examples of lifting a box or a bag up or throwing a ball or riding a roller coaster, we see that PE and KE are in effect and that work is applied to all of them, except riding a roller coaster.  SORRY FOR SOME REASON BLOGGER ISN'T UPLOADING MY IMAGES.  How do yours' work?

Physics is Fun and so is Friction

Friction is fun, yes it is.  Friction first of is noted as "f", a little f so as not to be confused with the big "F" of force.  f=(mu)(normal force); mu is pronounced as "mew" as appears as a lower case "u" with a longer first stroke, thus f=un (the u is the mu-best attempt).  Friction as defined as "a force that resists the motion of one object sliding past another."  Friction enables us to walk, run, and sit.  If there was no friction we would slip and slide and not be able to stand up.  Friction can be broken up into static friction, a "force that resists the sliding motion of two objects that are stationary relative to one another" and kinetic friction "when an object slides along another".  Static friction requires more force to overcome it and make the object move.  Kinetic friction requires less because the object is currently in motion and has moving inertia.  This explains why it is harder to get things moving at first then it is to continue to move said object.  In the background, I am moving the block of wood up the wall.  As stated in the definition of friction, in this example, friction would be working against my force in a downwards direction.  Conversely if I were to hold the block in place the block would want to move down and friction would then be upwards.  Not the best example of friction, I'm sure, but this just goes to show that Physics is always all around us and sometimes goes unnoticed.

Newton's 3rd Law and its Numerous Applications

Sitting around wondering what to do for my journal I realized that any picture I could possibly take applied to Newton's second law.  BTW: the reason for the exact same picture setting is not only for my convenience but also to show how physics can relate anywhere even right at home.  Moving right along, Newton's second law is defined by Kinetic Books as "A change in motion is proportional to the motive force impressed and takes place along the straight line in which that force is impressed."  As seen in my picture that blogger was not letting me upload, but hopefully by the time I post this it should be up there.  Anyways, the clear box I'm holding up has a net force acting upon it, or the sum of the force impressed by me carrying it and its weight of the box opposing my force.  The force of holding up the box would be signified as an upward arrow labeled with a "F" pointing up from the box.  The weight or mg would be pointing just the opposite.  The equation net force equals mass (of the object acted upon) and the acceleration or acceleration equals net force divided by the mass can help find anything having to do with Newton's second law.  In fact, this equation is the epitome of the second law expressing all the factors engaged in any action thinkable.  (well mostly)  In the picture this extends to all the objects, even me.  On anything that  is moved there is always at least two always acting upon it; the force applied to it i.e. push, pull and the weight of the object exerting its own force, both of these added together is the net force.  If the force applied is greater then the mg "all other things held constant" (ceteris paribus) the object will move.  If it is less the object will stay where it was.  So a net force is being applied in my picture to the box, to me, the chair, the shelf, the trophies, the book, and all other items you can name.  Hah well that's it for this journal, have fun with your journals and look out for Newton's laws in action!

Free-fall and a Ping Pong Ball

Journal 2: Recently, learning about free fall acceleration, I grabbed a ping pong ball and demonstrated this concept at home by simply dropping a ping pong ball.  "Free-fall is the rate of acceleration due to the force of gravity."  Ideally, in a vacuum, this acceleration would be exactly negative 9.8m/s but taking air resistance into account, the free-fall acceleration of the ping pong ball is a little less than that.  The acceleration of the ball and all objects is stated as a -9.8m/s when dealing with free-fall due to the downwards direction of the falling object.  Free-fall also applies to objects that are thrown up into the air.  These objects (assuming they will come down, hence excluding balloons etc.) may have a positive velocity but their decreasing acceleration as the object slows down to gravity will always be around -9.8m/s when they come falling back to earth (ignoring air resistance).  Free-fall can be seen in action with jugglers and any object that can be thrown into the air or dropped down (again ignoring air resistance).  Sorry, not much else here for free-fall, its pretty clear and clean cut, oh except that question on page three of the test. That was a crazy free-fall question. You all should know what I'm talking about... I hope everyone took the test.  Ok, that's all and just a reminder, all of you, do your journals!

Velocity, Acceleration, and Airsoft

Journal 1: When I discovered that we had to type Physics journals I immediately thought of Airsoft.  To maintain and check the reliability and efficiency of my gun I cleaned out the mechbox, or the part of the gun which utilizes a "battery powered motor to operate a a spring and piston set-up in a gear box." - (http://www.geocities.com/wajoegween/index.htm  The mechbox essentially powers your gun via the battery to shoot the airsoft bb's (pellets).  When shooting my G3SAS in the backyard I noticed the physics concepts of velocity and acceleration in action.  Velocity is defined as the displacement of an object over the time elapsed, shown in the equation: delta x/ delta t.  Displacement is basically the direction and distance of the shortest path between the initial and final position; represented by the final position minus the initial, symbolized by delta x.  Acceleration is the change in velocity, either wise shown as delta v/ delta t, or the change in velocity over the change in time.  When the gun mag is first inserted, the bullets are at rest with 0 velocity as well as 0 acceleration.  However, upon turning off the safety and switching to full automatic, a stream of bb's rapidly shot out of the gun.  The bb's initially have positive velocity, traveling in a forward direction, as well as positive acceleration.  My gun is able to deliver bullets at around 450 feet per second (fps).  This is the average speed of the bullets fired from my gun and also gives an indication of a gun's power; the higher the fps, the stronger the gun, the farther the bb travels.  At some point however, the bb's will slow down and decelerate, thus it will still have a positive velocity but will have negative acceleration, the bb's will travel forward but will be slowing down.  The bb's may reach the extent of their path and fall and hit the ground or will hit someone or something.  In either case the bb will come to a stop and effectively remain at rest, unless some other force moves the bb.  I hope this example has shed some light on velocity and acceleration as well as pique your interest.