Physics Archives - Page 21 of 27 - Educational Innovations Blog

Thermal Conductivity: If you Want a Good Thermometer, Don’t Use Your Body

November 26, 2011

by: Martin Sagendorf

An Easy Question: Which is warmer – which is cooler?

In the strictest sense, it’s a matter of energy. And we use temperature as a measure of energy level. As we all know, the greater the energy level, the higher the temperature… But, although this is absolutely true; sometimes it’s not exactly what we perceive in everyday life. When asked, we all can testify that when we touch a piece of metal we’ll say it feels cold. But is it really cold? Is it or isn’t it ‘cold’?

The Answer Is…

… very simple. If the piece of metal is at room (ambient) temperature it cannot be ‘cold’ – it must be at the same temperature as the temperature of the room.

But First:

Let’s discuss ‘perceived temperature’: this is what we ‘think’ the temperature is. It isn’t always the actual temperature (of the object we touch). Thus we enter a wonderful combination of both physics and biology. Physics describes the absolutes. Biology describes the biological reactions (interpretations) of our physical world.

It’s a matter of thermal conductivity and our nerves. Some materials are good conductors of heat (energy) and some are not. Our nerves sense only temperature – so if thermal energy is rapidly removed from the tissues surrounding our nerve endings (like at our finger tips), our nerves sense that the temperature ‘they feel’ is cooler – e.g. the material is removing thermal energy from the body tissue surrounding the nerve ends at a rate faster than our body can re-supply energy to the tissues – thus our nerves sense this as ‘cooler’.

Now:

A truly illustrative and memorable way to present the question: Read the rest of this entry »

Leave a Comment » | Biology, Elementary level, High School level, Middle School level, Physics | Tagged: conductors, discrepant event, heat energy, insulators, perceived temperature | Permalink
Posted by Tami O'Connor

Make Your Own Clock Faces

October 10, 2011

by: Martin Sagendorf

A Definition:

Clocks measure time – it can be a continuous measure of events passing or the measure of the interval between two events.

Of Hours:

After years of evolution, our modern clocks now divide the day into 24 equal length hours. And, as we know, there are two systems in use today: Americans use the “double-twelve” system while the rest of the world uses the 24 hour system.

As An Aside:

The word “hour’ comes from the Latin and Greek words meaning season, or time of day. A “minute” from the medieval Latin pars minuta prima (first minute or small part), originally described the one-sixtieth of a unit in the Babylonian system of sexagesimal fractions. And “second” from partes minutae secundae, was a further subdivision on the base of sixty – i.e. “a second minute”. (ref. Pg. 42 The Discoverers by Daniel J. Boorstin)

The “Double-Twelve” Clock Face:

Has 12 at the top – probably because at noon the sun is at its highest point in the sky.

But…

We can make a clock with 12 o’clock anywhere we wish and the clock will still work just fine. Read the rest of this entry »

2 Comments | Chemistry, College level, Elementary level, High School level, Middle School level, Physics | Tagged: clock making, homeschool, interesting clock, parent friendly | Permalink
Posted by Tami O'Connor

The Law of Dulong and Petit

September 3, 2011

by: Dr. Jean Oostens

Atoms were proposed in antiquity without any experimental evidence by Democritus, a Philosopher. This must have been a problem for Newton and Leibnitz who posited that there was always a mean of considering smaller and smaller intervals of space to calculate the “instantaneous velocity”.

The introduction of the precision balance in chemistry by Lavoisier paved the way for Dalton to formulate his laws on the “definite and multiple proportions” governing chemical reactions. This supported the atomic theory, without giving it general acceptance.

Specific heat was defined as the quantity of heat needed to increase one gram of a substance by one degree. There was no definite pattern when specific heats of various substances were compared. Until two French scientists in 1819 calculated specific heat by atomic mass, forming the Law of Dulong and Petit. There appeared a number of cases where the results were quite similar: about 6 calorie per mole. This was equivalent to stating that any atom is as good as any other to store heat! This was a small step towards acceptance of the existence of atoms. An explanation for this, and the reason for the exceptions, had to wait the early 20th century explanation by Albert Einstein. By that time, atoms had gained wide acceptance from the work of Rutherford, and soon by Bohr.

Lesson on the Law of Dulong and Petit:

You are given several chunks of metal, each containing 0.6 * 10²⁴ atoms (i.e. one mole) of one element. How will each of those samples, when dropped in a standard quantity of hot water (typically 200 mL and 70 C) affect the temperature?

Step 1. Use a good balance (at least 0.1 gm resolution) to determine which element you are dealing with. If possible confirm your identification with an additional cue. Read the rest of this entry »

1 Comment | Chemistry, College level, experiments, High School level, Physics | Tagged: Chemistry, Dulong and Petit Law, metals, mole, specific heat | Permalink
Posted by Tami O'Connor

How to Make a Rocket (Scientist)

July 1, 2011

by: Tami O’Connor

A few months ago I had occasion to conduct two hands-on workshops for elementary and middle school teachers at the NSTA National Convention in San Francisco on behalf of Educational Innovations. One presentation focused on film canister rockets. This is a tried-and-true way to teach Newtown’s First and Third Laws of Motion and also brings to light concepts such as the four forces of flight; thrust, drag, weight, and lift. It also reinforces instruction on 3-D shapes and 2-D plane figures such as circles, cones, cylinders, rectangles, and triangles.

I presented the lesson to the teachers in much the same way I would to my students. The first thing we did was to brainstorm the features all rockets have. After a bit of discussion it was agreed that they all have a nose cone, a cylindrical body, fins, and an engine. I then handed out a paper template imprinted with the pattern of a nose cone and fins, a regular 8½ x 11 sheet of white paper, a piece of goldenrod paper, and a white translucent film canister. Also required are scissors, tape, ¼ piece of an Alka Seltzer tablet, and paper towels.

The only canister that works with this rocket is the type that has the lid that fits snugly inside the canister. The canisters that have a lid that wraps around the outside rim, however, will not allow enough pressure to build up inside the chamber.

How to Make a Rocket

The first step in building a film canister rocket is to construct the body of the rocket. The easiest way is to curl the white 8 ½ x 11 paper into a cylindrical shape using the film canister (without the top) as a guide. The paper can be rolled around the film canister and then taped along the edges. The easiest way to recover the film canister is to blow into one end of the rolled cylinder, forcing the canister out the other end. Read the rest of this entry »

3 Comments | Chemistry, Elementary level, energy, experiments, High School level, Middle School level, Physics | Tagged: Alka Seltzer rockets, energy, film canister activities, momentum, parent friendly, PBL, phenomenon based learning, phenomenon-based science, rockets, science, STEM | Permalink
Posted by Tami O'Connor

Newton’s Apple

May 28, 2011

by: Matthew Morris

Newton was a revolutionary thinker of his time. He is responsible for the three laws of motion that we still use today;

1. Objects that are not in motion remain stationary unless acted upon by another force.

2. There is a direct relationship between the force acted upon the object and the mass of that object times the acceleration the object feels (F=ma).

3. For every action there is an equal and opposite reaction.

Nobody before Newton could explain why objects acted the way they did, but with these three laws he quantified movement in terms everyone could understand.

But there was a problem with his theory; if all motion had to be caused by some force acting on it, then why do objects fall towards the earth when you release them from a fixed position? This free falling object was in fact free, meaning free of outside forces acting upon it (besides wind resistance). There were no visible forces acting upon that object. So why do they move downward if nothing is acting on it? But Newton explained this motion with gravity. He said that gravity is a force that the earth has upon all objects, something invisible that pulls us down at all times at a constant acceleration. There is a myth that the way Newton thought of the idea of gravity was when he was thinking about it under an apple tree when an apple fell on Newton’s head and at that moment, he figured out that there must be a force pulling the object down. This is also why apples are used to demonstrate Newton’s force, but no one knows definitively if the myth is true or not. Read the rest of this entry »

Leave a Comment » | College level, Elementary level, experiments, High School level, Middle School level, Physics | Tagged: acceleration, awesome experiment, force and motion, gravity, Newton's Apple, PBL, phenomenon based learning, phenomenon-based science, science, Sir Isaac Newton, spacetime | Permalink
Posted by Tami O'Connor

Educational Innovations Blog