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.