Center of Gravity

 

Textbook Story

- Professor, do you need the textbook?

- No, I do not. Whether YOU need a textbook, that is a different question.

Physics and recycling

Physics and recycling don’t appear to be connected at first glance, but after a closer look, it is easy to see that physics plays an important role in looking after our planet.

Recycling is critical to our environment.  Plastic bottles, paper and cardboard, aluminum and metal cans and glass jars take up so much land fill and can be easily recycled and re-used.  All these materials take energy to create and produce. By manufacturing these costly materials damages our planet by releasing toxic gases into our atmosphere. 

Recycling is a way that everyone can help our planet. By turning the waste into re-usable items cuts down on the amount of products that need to be produced.  Paper can be made into a pulp and recycled for newspaper or cardboard.  Plastic and glass can be made into new plastic and glass items.  Aluminum and metal can be recycled into new cans and items.  Once the recycled waste is separated into plastics, glass, metal, and paper or cardboard, then the laws of physics come into play!  We use gravity, conduction, magnetism and electromagnetic waves to recycle.

• Gravity is the force that pulls everything down towards the earth.  By creating a group of holes (large and small) and spinning discs makes it easy to sort through the recyclable items. This is physics in action!  This incline of vibrating, spinning rubber discs acts like a giant sieve and sorts items according to weight. The heavier items, such as metal and glass will fall to the bottom and the lighter items like plastic and paper will be at the top.  
• It is important to separate metals and aluminum to be melted down because steel and aluminum melt at different temperatures and have different magnetic properties.  Some metals are ferromagnetic, which allows them to be pulled out with a magnet while other metals need a machine called an “eddy current separator” so we need to induce magnetism to sort the aluminum.  Ferromagnetic items are steel and easily attracted to a magnet but drink cans are made from the metal aluminum, which is not ferromagnetic. The eddy current separator is the technology that uses a rotating drum lined with rows of magnets, creating magnetic fields which separate aluminum from other metals.
• All metals, aluminum and steel conduct electricity and their specific magnetic fields create the electricity inside the metal recyclable items.  It is because of the physics of electromagnetic waves that we can successfully separate the materials to be recycled.

Tim

Metaphysics Applied to Students' Life

 - Professor! This is the last lab this semester.  Do you still want us to come? 

Well, I am thinking about what to answer.   

Dear Student, not really. For me, you do not have to come to class.  In fact, you do not need to get up off a couch if you do it for me. 

What you can do for me, is to think about your life, which begins with your education, and figure out how much you want to benefit (or not) from attending this course.  When you know that, make an informed decision about coming or not coming to class.

Lecture vs Lab

Student:     Professor, there is something wrong with this lens.  I cannot find the image.

Instructor:     Is it a converging or diverging lens?

Student:     Diverging.

Instructor:     So, should you see the image formed on the screen?

Student:     I dunno...

Instructor:     Well, it was shown in my presentation 5 minutes ago.

Student:     I saw it, but I didn't think it was for real!

Sunburst

The diffraction of light causes an interesting effect in photography.  The light waves bend on the camera lens and interfere causing lighter and darker spots.  These lighter and darker spots form patterns of lines like the one visible in the picture above.  Nice.  A friend of mine made that picture in Italy, at the Tyrrhenian Sea.