MORE Physics Games

There's a whole website dedicated to Physics games online: http://www.physicsgames.net

Collisions Video

Excellent video that clearly shows the difference between elastic and inelastic collisions.

WATCH HERE!

Cool Telescope Stuff

I found two really neat resources about telescopes.

The World Wide Telescope was developed by Microsoft and allows you to see into space with a simple, downloadable computer program.

A recent article in the English newspaper The Independent describes how the world's largest telescope can see so far into the past, Einstein's theories will be tested! Check out the article HERE.

Great Java Simulations for Science Class!

The University of Colorado Boulder has a fabulous site for interactive science simulations.

In one of my favorite simulations, you can create a circuit using light bulbs, wires, resistors, batteries, etc. as well as household items such as a dollar bill and a paper clip. When the circuit works, the light bulbs light...the more resistance, the dimmer the lights.

Loads of other great simulations HERE!

Optics Resources

In writing a unit plan for optics (coming soon) I stumbled upon this website: http://library.thinkquest.org/C003776/ingles/fun/index.htm

The site is full of activities geared towards optics as well as java applets and other media resources. Enjoy!

Rutherford Gold Foil Experiment

A friend showed me a fabulous lesson plan to teach about Ernest Rutherford, his atomic model, and his gold foil experiment.

She began the lesson by playing a game to help students estimate the size of something they can't see. Inside a large box (the cave), she placed a can (the monster) and cut slits out of the bottom of the box so students could slide checker pieces through. Analogous with Rutherford's gold foil experiment, most checker pieces slide straight through while some bounce off the "monster" at small angles and others bounce backwards. This is to help students understand how Rutherford determined the nucleus of an atom must me massive and dense.

Then, she showed the animation found on this website that explains Rutherford's experiment. A great way to discuss the atomic models!!

Physical Sciences Resource Center

Great website for teacher resources relating to the Physical Sciences: http://www.compadre.org/psrc/

Physics Games: Bubble Quod

I was browsing some internet games this evening and found this game. Great for discussions on momentum, center of mass, and basic mechanics!! The object of the game is to move your bubble up and over obstacles, ramps, and levers to the rusty nail in order to pop the balloon!

Bubble Quod

National Science Teachers Association

Here's the link for the National Science Teachers Association.

This website is great for resources. They have up to date articles on science and education in the U.S. as well as a comprehensive bookstore which includes some free resources!

Roller Coaster Physics

I found this website awhile back and can't believe I forgot to share it!

Amusement Park Physics: What Are The Forces Behind The Fun?

The Roller Coaster activity is a lot of fun. I used this first with some of my peers in Graduate School and they loved it :o)

The gist of the activity is your students (or your whole class) choose from different selections for the different parts of the roller coaster: hills, drops, loops, etc.

Try it out!

Seeing Sounds

If you've never seen this demonstration, it's incredible.

This is called a Chladni Plate. Originally, a man named John Tyndall found that the different frequencies at different pitches caused different patterns of sand to emerged. His patterns (seen HERE) look much different than the video because he used a bow against the side of a plate and created nodes with his fingers. Modern Chladni plates work due to a motor attached at the middle of the plate (the node) and a speaker that plays the different pitches.

For directions on how to make a Chladni Plate, google "How To Build A Chladni Plate". There are many great resources!

Vacation Science: Hoover Dam

I was recently out in Las Vegas visiting my college roommate. My one tourism request was to see the Hoover Dam. My wish was granted and my friend and I hiked along Lake Mead all the way to the Dam. We went on the Power Plant Tour and saw the new bridge being built! It was very exciting :o)

The Power Plant Tour was excellent! We were privileged to see the generators at work as well as the massive pipes through which thousands of gallons of water flow through every day! We had excellent views of the Dam as well!! A new bridge is being built to allow the highway to bypass the Dam since the road passing over it winds through the mountains at 25 mph. The bridge was fascinating and promises to be one of the best views of the Dam!

The tour and museum were excellent educational resources. In the generator room, one of the generators was dissembled for maintenance - a phenomena that only occurs every 25 years! The rotor (the big wheel with large magnets attached all around) was just lying on the floor. It weighs almost 6 tons and took two huge cranes to move it from its normal location.

The museum also did an excellent job of explaining how the generators work! I have included pictures below to help explain:

This is a scale model of a generator. The water flows in the clear tube into the small dark green squares. These channels are openned and closed depending on the amount of water to be let in. As the water spins (sort of like a horizontal water wheel), the metal rod you can see in the middle of the picture begins to spin (this is the shaft). The shaft is connected to the rotor (the round part at the top which appears to have silver Lady Finger cookies attached) and the rotor spins as well. 

Surrounding the rotor is coils of copper wire. From Physics, we know that when we pass a magnet through a coil of copper wire (known as a solenoid) the magnet field changes. And where there's a changing magnetic field, there's current flowing.

So...to sum it up, the water makes the shaft and rotor turn, which causes the magnets to move past the coils of copper wire, causing a changing magnetic field, resulting in a current, or flow of electricity.

To top it all off -- the Hoover Dam wasn't even built to serve this purpose. It was created to aid farmers in irrigation and creating hydroelectricity was the only way to pay off such a massive project built during the Depression!!

I am seriously considering teaching Electricity & Magnetism units using the Hoover Dam so students can understand the real life applications!

Vectors

I was teaching centripetal acceleration to my 10th grade sister several weeks ago. I used the race car on a banked curve explanation in another blog entry. We got to the end and she said something to the effect of, "Oh, I get it. That makes sense. Except -- what's a vector?"

I had to think for a moment. Outside of the physical science and mathematical world, what is a vector?

Finally I explained it as follows:

You're having a picnic at the park. Just as you're about to leave, you realize you don't have any mustard for your hot dogs. So...you go to the store on your way to the park. Or...you could have just checked the back of the cupboard and realized you had some. Then you can just go straight to the park.

But the main thing is: you still made it to the park, right? So regardless of whether you stop at the store first, or not, you still have a picnic at the park.

My sister's face lit up as she realized vectors were not the same as triangles (she's currently in geometry) and she acknowledged that vectors and their resultant are all different ways of expressing the same thing.

Mathematically:

2+3+1=4+2=6

The Color of Light

I saw a great demonstration the other day in class about the color of light. It is similar to a lesson plan found at: http://science.hq.nasa.gov/kids/imagers/teachersite/UL1.htm

To begin, my classmates drew two venn diagrams. One had the colors of paint (red, yellow, and blue) and the other had the colors of light (red, green, and blue). We guessed which colors created which new colors (orange, green, purple and yellow, cyan, and magenta, respectively).

Next, they turned on three light bulbs (a red, green, and blue one). All other sources of light was covered and a large white projection screen was against one wall. One classmate put a meter stick in the way of the light and in front of the screen. It was amazing to see the meter stick separated the light into yellow, cyan, and magenta. Then the light bulbs were turned off one at a time. When the red light bulb was turned off, the background of the screen was cyan, while green and blue were separated by the meter stick. Similar results occurred when the green and blue light bulbs were turned off. 

It was just amazing!! Try it at home if you don't believe it :o)

Careful, don't fall off the Earth!!

In class the other day we calculated the minimum acceleration we need to stay on the earth...what we found was fascinating!

First, we need to discover the diameter of the Earth as well as the time, in seconds, it takes the Earth to rotate once:

d=2*pi*radius=2*pi*6.3781 x 10^6

d=4.007 x 10^7 m

t=24hrs=1440min=8.64 x 10^4 sec

Now we have a change in displacement and time to calculate velocity:

v=(distance)/(time)=(4.007 x 10^7 m)/(8.64 x 10^4 sec)

v=463.77 m/s

We know the acceleration in circular motion is a=(v^2)/r, so plugging in the velocity and radius will give us the minimum acceleration of one point on the Earth without anything flying off!

v^2=2.1508 x 10^5 m^2/s^2

a=(v^2)/r=(2.1508 x 10^5)/(6.3781 x 10^6)

a=0.0337 m/s^2

So, we can see the minimum acceleration needed for us to stay on the Earth's surface is much smaller than the 9.81 m/s^2 acceleration we experience every day. This is the exact reason why we are able to fall down.

Imagine if the centripetal acceleration were only .0337! We would merely hover over the surface of the earth -- how crazy!?

Physics Jokes: Chickens

Why did the chicken cross the road?

Isaac Newton: Chickens at rest stay at rest. Chickens in motion cross roads.

Albert Einstein: It depends on your frame of reference, how do you know the road is not crossing the chicken?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

There is this farmer who is having problems with his chickens. All of the sudden, they are all getting very sick and he doesn't know what is wrong with them. After trying all conventional means, he calls a biologist, a chemist, and a physicist to see if they can figure out what is wrong. So the biologist looks at the chickens, examines them a bit, and says he has no clue what could be wrong with them. Then the chemist takes some tests and makes some measurements, but he can't come to any conclusions either. So the physicist tries. He stands there and looks at the chickens for a long time without touching them or anything. Then all of the sudden he starts scribbling away in a notebook. Finally, after several gruesome calculations, he exclaims, 'I've got it! But it only works for spherical chickens in a vacuum.'

Why Raindrops Don't Kill Us...

I'd never really pondered the idea that raindrops might be a cause of death until the other day.

If we're concerned about killer pennies from the top of the Empire State Building, how much more scary are little water bombs from thousands of feet in the sky?

No need to fear...physics is here!!!

Since raindrops are relatively small in volume, the reach a small terminal velocity quickly. An explanation follows:

When raindrops fall, they are met with air resistance. Air resistance is proportional to surface area, so small and big raindrops experience the same phenomenon. The air continues to resist the raindrop until air resistance reaches the same value as the gravitational force. This moment is when the raindrop reaches its "terminal velocity". It can't go any faster because it's no longer accelerating. 

And since rain drops have little mass, they won't have a very large velocity!!

Good thing there's air resistance between the clouds and the ground!

Physics of Race Cars

In my Concepts in Physics course the other day at TC, we discusses race cars on a banked turn. We used free body diagrams (FBD) to illustrate where the centripetal force (the force that keeps the race car traveling in a circle).

Here is the basic FBD for a car on a banked turn. The dot in the middle of the rectangle (car) represents the car's motion out of the page and toward the drawer or looker.

So, we've got the car on the incline. The force of gravity is always directly down -- in the direction of a free hanging plumb line. The normal force (typically the force opposite the gravitational force) is always perpendicular to the surface, so not vertical in this case.

Now things start to get fun!!!!

We draw the components of the normal force in with dotted lines; pretty much, we're making the normal force the hypoten

use of a triangle. You can clearly see the vertical leg of the triangle is equal and opposite to the gravitational force.

Left over is the little bit of horizontal normal force. Notice that it is pointing towards the center of the circle...it seeks the center. The definition for centripetal force is "center seeking", so this must be the centripetal force on the car!!!!

The neat thing is, the faster the car travels around the bank, the higher it will go on the incline. The higher on the incline, the greater centripetal force. And the driver doesn't have to do a thing! All these things happen naturally :o)

I thought this was a great demonstration to show students where this mysterious and confusing force comes from. It certainly isn't magic!!!

Physics In The White House

I just read this article that President-Elect Obama has named Physicist Steven Chu as head of energy -- yay Physics!! This would be a great current event for students in the classroom to see how physics effects their every day lives. :o)

Link to Article

Centripetal Acceleration Proof

I took notes on this proof the other day while observing Mr. Provo and Mr. DePalma team teach:

Start with a circle with the velocities pointing in the tangential direction to the circle. Draw the radius so students can see the velocity is perpendicular to the radius. Label the angles and radius so students can see they are the same (even if one angle is larger, it means the arc covered in that time is longer).

The next step in the proof is some vector addition. Placing two vectors together (not using the initial vector since it has no vertical component), students can find the direction and magnitude of the acceleration. According to the image below, the acceleration will be toward the center of the circle.

This triangle (when drawn well) will be a similar triangle to those in the circle. This means we can create a ratio.

The arc(ab) can be written as the velocity multiplied by the change in time - the circle image. Therefore, the first part of the ratio can be written as v*(delta)t/r. The triangle diagram shows the change in velocity divided by the magnitude of the velocity is analogous to the first part.

v*(delta)t/r ~ (delta)v/v

Now we want to get the deltas on the same side.

(v^2)/r ~ (delta)v/(delta)t

And we know that (delta)v/(delta)t is also equal to acceleration. So...

(v^2)/r ~ a

But, this is only an approximation, so we've got to figure out how to make it exact. Well, as the angle between the vectors approaches zero (again referring to the circle diagram), the arc(ab) approaches a straight line. And as the change in time approaches zero (as measurements become more instantaneous), the velocity becomes perpendicular to the acceleration. This means the approximation we made can be exact - both the velocity and radius are perpendicular to the acceleration.

(v^2)/r = a !!!

This isn't the most clearly written proof, but I'll work on it.

Things to remember:

- As velocity increases, so does acceleration.

- As the radius increases, the acceleration decreases.