LESSON REVIEW #  11B: The physics of falling bodies, pendulums and objects in motion.

           

                              Cleophas Mike McAlpin......Tutor

    We did it!  Lesson Review….."Falling Bodies"

Date: November 29, 2000                             Time: 3:00PM-8:30PM

          A matter of "G": the Universal Gravitational Constant

It was difficult to drop a “D” battery from the ceiling of our family room and measure the time that it takes for it to hit the floor, but we did it. We did it, that is, with a reasonable degree of accuracy, having done it at least ten times, and after having averaged those ten times. The time that it took for the battery to hit the floor was calculated as 0.70 seconds, or 70/100 as our stopwatch indicated. The measurement of distance from the ceiling to the floor was done by Jeremiah (12) and found to be 95 inches, which he promptly changed into feet by dividing by 12. He then multiplied the feet by 0.305 to change them into meters.

Jarrell (13), James#1 (12), Jeremiah (12) and James#2 (15), tried to drop the battery and measure the time. They found it difficult because human reflexes are just too slow to react to pushing a button one time (when they let the battery fall), and pushing a button again when the battery hit the floor. As a matter of fact, I used this fact to let them know that tailgating while driving a car is dangerous because of this lack of human response time.

Of course, each of the students knew that a report had to be made on our Physics lesson for the day.  Even though Sheena (14), Cleasena (14), Cassandra (13), and Matthew (14), arrived in the middle of our experiment, they knew that a report in Microsoft word had to be done and turned into their respective Middle and High School teachers for extra credit. Perhaps that is why they paid strict attention to the formula:  S=1/2 GT 2    where “S” is the distance that a body falls (our battery or any weight); “G” is the acceleration of that body due to gravity; “T” is the time that it takes for the body to fall that distance.

 After our measurement of time and distance, it was time to put those quantities into our formula for “S” and calculate the acceleration due to gravity, “G”. It was time for Algebra.

Jarrell, James #1, and Jeremiah came up with 32.2 feet/second2 , or 9.8 meters/second2.  All of the Physics books that I have ever seen give those same English and Metric values for “G”!

What did the students learn about Physics and Algebra in a very short time? What did they accomplish in the one hour that I gave them to absorb all? How did they feel when they came up with the correct answer to “gravity”? Did some of them complete their report? Did all of them understand that a body that is falling does not maintain a steady velocity, but accelerates at 32 feet per second, every second, until it hits the ground? Did they learn that astronauts are able to float around in space because of this lack of gravity some 200 miles above the surface of the earth? Did they learn that it is akin to everything on the surface of the Earth being tied to a giant rubber band that pulls back when a body tries to leave the surface? Did they learn that a body must move at a velocity of 7.2 miles per second to leave Earth's gravitational pull? Did they learn anything about spacecraft and booster rockets? Did they learn about how to solve an Algebraic equation that has two of three unknowns given to them? You bet they did!

 Yes, it was a very intense lesson. Most of the students paid strict attention and absorbed all. They were very excited and interested in the experiment and the results that followed. They really enjoy timing things! Especially when the “time” can be used to calculate a universal constant such as “G”. Yes, they did it! It leads me to wonder if they will ever get tired of calculating this “G”. After all, they did it at the Griffith Observatory just a few weeks ago when they timed the Period (T) of the Foucault pendulum in the lobby. They used another formula: T= 2pÖ L/G,  to calculate “G” and came up with the same value. Be sure to click on "Pendulums".

 The lesson continued on into…”A Ride on a Slide”.  This time, a little girl on a slide was used to calculate “G”.  Her weight didn’t matter, as the students found out. Only the frictional force that held her back and the angle of the inclined plane (slide) mattered. Sheena (15) had been pounded with this knowledge until she must be an expert by now at finding the acceleration of a little girl and a slide, or any body that is moving down an inclined plane. Sheena and I have pounded that Physics lesson until we could teach it in a University. We reviewed our lesson with the rest of the students.

 Any unbalanced force has acceleration attached to it. That I why someone came up with the formula F= MA. The little girl moving down the slide has an acceleration (A) attached to her. I was our job to calculate that acceleration from the formula. First of all, though, we needed to find the “F”.  That involved drawing a diagram of the forces acting on the little girl. There was the Frictional force (FR), and the Normal force (FN). There was her Weight (mg) and a frictional constant,  Mu (m). There was the Mass (M), which really didn’t matter at all because bodies moving toward the Earth under the influence of gravity are not too considerate of weight.

 A previous lesson review (1 week) outlines the “Ride of a Little Girl on a Slide”. Please review this lesson review for a complete picture of the forces acting on her. You will reach the conclusion, just as Sheena did, that her acceleration moves towards 9.8 meters/second/second as the incline moves toward 90 degrees. Sheena’s experiment with a “d” battery ( “d” battery? The first object that we saw) sliding down one of our tutoring tables that had been inclined to approximately 40 degrees. 

Of course, MGCOSq, F= m N, W=MG, FX =MGSINq,  C2 = A2 + B2 , F= MA, are all of the formulas that are necessary to calculate the particulars of the girl’s ride, even when she reaches back to slow herself down.   Last month, it was the “Biology Blitz”. This month, it is the “Physics Blitz”…of the Free Tutoring Service.

James #2 probably has a mental block against multiplication tables. That block is being rapidly removed as I work with him on basic fractions, on a constant and intense basis. He is very astute, otherwise.  Cleasena needed little homework assistance as she did an assignment in English. Sheena worked on a “sonnet” for English class. Cassandra worked on Algebra and I assisted her with solving equations. Mathew listened as I reviewed him on Algebra, also. James did fraction problem after fraction problem for me. Jeremiah, James and Jarrell were sent to the Computer station # 2 to input their voices into the Windows Recorder in the Spanish language and then saving them to a file. They laughed at themselves in their attempt to say Spanish phrases. We are deep into learning Spanish, both from our Volunteer Tutor, Mrs. Marci Williams on Sunday afternoons, and our CD-ROM disks when she is not present. The three future scientist were sent to Microsoft Word at each of our three computer station to finish their report on “falling bodies”.

 I took the students home. It had been a very long day. I had spent long hours working on a website, www.nuphilly.com for New Philadelphia Church Family in Carson (my church). I had spent long hours finding out how to do this and do that with regards to the site. I had spent long hours because the students of the Tutoring Service will become “Webmasters” just as I am attempting to become…in my very little spare time.  They are well on their way with their knowledge of the computer, as our previous lesson reviews remind us, and they are poised for the future. That is precisely what we are doing, with the Power of God within us…preparing our children for the future.

 Nothing will stop us in our quest. Not man, nor money. We will survive to teach our youth, no matter whether we receive financial assistance or not. We will make any sacrifice to keep on moving. Are you complaining about the state of our youth, or are you doing anything to help? Are you teaching them any moral values or any educational values? Are you, as a parent, standing in their way by not becoming involved in their schooling? Our conscience is clear.  Visit this website often and you will find out why!