First Semester Physics Examples
home:
An Air Track and Newton’s Law Lab
This part of the page will ask a few probing questions and offer a few terse answers. If you are a student here and want more explanation, please ask me and this may help me improve on this site.
When one is working with Force equals the mass times acceleration, which force should one use? Isn’t the glider on the air track being pulled by the tension of the string? Is the tension in the string equal to the weight of the masses on the string?
Answers: The tension is not equal to the weight of the masses if the glider has a none zero acceleration. There are many approaches to the problem, two of them are:
The Tension (the force on the glider) equals the mass of the glider times the acceleration of the glider
The Weight of the masses (the force of the system) equals the mass of the system times the acceleration of the system.
When the force of the hanging masses on the system is calculated the weight is used. Why? Why is the weight of the mass equal to the mass times an acceleration equal to 981 cm/s^2, when the mass isn’t even moving?
Answer: Look at the topic of Universal Law of Gravitation in the text book. The force of attraction is actually being considered.
A 9 Foot Tall Manometer
This part of the page will illustrate topics and tell a few related stories.
This is an example that brings up pressure as a function of depth and then digresses into two thought provoking examples.
A few relevant items to illustrate the topics related to this manometer.
1. This manometer allows one to determine Atmospheric pressure. Torricelli was reported to have had made a large manometer (a barometer) that was in his chimney. He put small dolls in the water and they would float on the surface of the water and move as the atmospheric pressure changed. In fine clear weather they would float to the outside, in bad weather they would float back into the safety of the chimney. Fact is more fun (and stranger) than fiction: See what the results of his work were from the web. try key words of Torricelli, barometer and floating wooden dolls. If you find the right sources you will find that he was forced to take it down. Remember it was the 1600s! (remember Salem Mass.)
2. Once more, this shows pressure as a function of depth. There is a local legend that an Instructor was lecturing about pressure on liquids. One “smarty” student raised the point to his instructor in class, that if this were true then if everyone in his dorm were to release the water in bathrooms at the same time then the pipes would explode. From the web I found these words “logical that the pipes would most definitely rupture in multiple places causing total failure of the sewage system” Although I do NOT advocate this, use this as a learning tool :-)
This is here for the purpose to illustrate an example of how a thermal engine can be modified with the second law of thermodynamics.
A link to a YouTube video on 6 cycle engines is shown: There are some clever people out there right now showing their ideas. More power to them.
This seems to be an important development in engines. Think of the amount of thermal energy that will not be lost and instead put into mechanical energy. Our labs experiment p4 and p5 teach thermal energy and pressure, temperature and volume
This engine design uses the hot engine walls to heat water injected into the cylinder and then the water turns to steam and exerts a force on the engine’s piston. This is where “cycle 5 and 6″ come into the ordinary 4 cycle engine. This creates an engine that is both internal combustion engine and a steam engine. An interesting use of thermodynamics and it could be a “green” use of the thermal energy that would normally be wasted.
This is here an interesting YouTube video on the 6 cycle engine. I hope the work of these people inspire someone to take this to large scale use.
Here is an example of a small 6 cycle engine on YouTube
See Youtube-6 cycle engine! Notice title appears when you roll over link, before clicking
