9-23-08

Frances Bruey The room quiets down as the last few people in Mr. Manning's physics class sit in their seats and listen. The topic for today is Inertia. A young, curious Frances Bruey asked, “What exactly is inertia?” The answer is quite simple. Inertia states that objects resist changes in motion. Inertia, proven by Galileo, disproves all of Aristotle's theories about motion. Aristotle believed the rate at which objects fell was due to their weight. Doubtful of this, Galileo dropped two objects of different weights off the now Leaning Tower of Pisa. He found that the two objects landed on the ground at the same time. He then did the inclined plane experiment. This is where he dropped a marble down the inclined plane and found it was very close to reaching the same height on the opposite side of the plane(a). Next he dropped a marble down a plane where the starting side was steeper the the opposite side(b). Galileo found that this time the marble reached the same height. Finally, he made a plane where the starting side was steep and the opposite side was horizontal(c). He found that the marble kept going.
 * __Mr. Manning Does it Again!__**

He concluded that it must be friction holding the object back from reaching the same height, and that an object will keep moving in a straight line forever. In the Leaning Tower of Pisa experiment, where there was no friction tied to the objects, the objects fell at the same rate. In fact, all objects fall at the same rate when friction is absent. There are many modern ways to prove this theory. Mr. Manning showed his class the infamous marble demo first followed by the water demo. This is where he took a beaker filled with water and placed a piece of paper underneath it before setting both of them on a table. Then Mr. Manning pulled away the paper quickly like a magician pulling away a tablecloth on a table. This is actually very scientific because it proves the beaker has inertia. This means the beaker was in a state of rest so it wants to continue to stay in that state of rest. The paper moved so quickly it did not disturb the inertia and the beaker stayed on the same place on the table. Another demo shown was the hoop demo. This is where Mr. Manning carefully balanced a hoop on a glass and then a marker on top of the hoop. By grabbing the hoop away quickly from the inside, the inertia was not disturbed and the marker hesitated for a nanosecond before falling right into the glass. As amazing as this trick is the most awing activity was the banana demo. The banana demo consisted of Mr. Manning holding the sharpest knife he owns in one hand and a banana in the other. Mr. Manning dropped the banana and quickly sliced through the banana while it was in mid air. He had to do this quickly because at first the banana doesn't move that fast due to inertia. The banana wanted to stay at rest so it resisted falling. But the banana then quickly picks up speed because of gravity. To sum up, Mr. Manning has a better chance of slicing through the banana if he does it quickly after he lets go of the banana versus waiting until it gets closer to the ground and has already started moving faster. One thing to remember about falling objects is that heavier objects have more inertia. This is due to Newton's 1st Law (the Law of Inertia). In this law Newton states, “ Every particle remains in a state of rest or continues in a state of motion with constant speed in a straight line unless compelled by an unbalanced force to change that state.” To put this in a mathematical statement, if there is no force acting on the particle then there is no change in the speed of the particle. To conclude the fun activity filled day, Mr. Manning finished with a video by the Julius Summer Miller (but the students refer to him as the crazy old guy). Mr. Miller mentioned how inertia and mass are synonymous. He also showed multiple demos that proved the same ideas Mr. Manning taught. All in all this reporter was impressed by the teachings of Mr. Manning.
 * Fnet = 0 then change v = 0**