What is RepRap?

The Makerbot Replicator 2 3D printer

We're excited about 3D printing at Yale High School. We've spent the last two weeks exploring different types of stuff we can make with our new printer. As I was reading about 3D printing, I came across a very interesting idea called RepRap.

1. What is RepRap? What does it stand for?
2. What are the initiative's goals?
3. What progress has been made?
4. What are the technical (or other challenges)?
5. Do you think this is an important idea? Explain your reasoning.

Thinking about the Science Fair

Photo used with creative commons license from jshontz

We've talked a bit in class about the upcoming science fair. One of the biggest hurdles for students to clear is coming up with an idea to use as a project. It's important to distinguish between a science experiment and a science demonstration. Consider the classic baking soda and vinegar volcano we often see depicted in TV shows or movies as "science fair projects."

I'd argue that the baking soda and vinegar volcano most likely is an example of a demonstration rather than an experiment. Let's discuss this idea a bit further:

1. What are the characteristics of a science experiment?
2. How does a science demonstration fall short of an experiment?
3. Would you agree with my judgement that the volcano project is more likely a demonstration?
4. Do some searching online of "science fair projects." Can you find other examples projects that students have done that are demonstrations? If so, provide the link in your comments.

Simple? Harmonic? Motion

Graph of sine from Wolfram|Alpha

We've been talking about pendulums, spring-mass systems, and how they relate to simple harmonic motion. For this week's comments, I'd like to hear some more about simple harmonic motion... ... Why is it called "simple"? What is simple about it. Also, what does the word "harmonic" mean in this context? Is it related to music at all? What are some other examples (besides those mentioned in class) or simple harmonic motion?

When the Normal Force is not Normal

As we learned about friction in class, we were introduced to the concept of the normal force. Many times, the normal force is exactly equal to the force of gravity on the object. However, this is not always the case. Can you think of any situations where the normal force is not simply equal to the object's weight? Leave comments with your ideas so that each idea is in its own comment.

Alternatively, do you have any questions about either the normal force or friction?

The Curveball

Photo by Sean Winters

I've been watching a lot of baseball on TV lately. I think it's amazing how professional pitchers can cause the path of their pitches to curve (or deviate from a straight-line path) radically. Here are some questions for discussion:

1. Many baseball terms exist to described pitches that curve. For example, curveball, screwball, slider, and cutter. What are the distinguishing characteristics of these pitches? Are there other terms that belong on this list?
2. What causes a pitch to curve (or break)?
3. Does the shape of a baseball affect how much it breaks? If so, what shape ball would break the most?
4. Does the speed of the ball affect how much it breaks?
5. Thinking about 3 and 4, what kind of ball could you use to demonstrate various breaking pitches? Ideally, the ball would be easy to throw and it would very noticeably break.

Thinking about Free Fall

We've been talking about free fall in physics class. Consider the following questions:

1. What are some examples of object that are in free fall (or at least "nearly" in free fall)?
2. Can an object be in free fall and have a velocity of zero? Explain.
3. Suppose the acceleration of gravity on Planet X is 20 m/s/s. How long would it take an object to fall to the ground from a height of 100 meters on Planet X? (Don't just give a numeric answer. Explain your reasoning.)
4. The acceleration of gravity on the Moon is about 1/6 as much as Earth's. Suppose an astronaut throws a ball up vertically with an initial velocity of 20 m/s. How high above the Moon's surface will the ball rise?  (Don't just give a numeric answer. Explain your reasoning.)

Select one of the above questions and leave your answer as a comment. You can also comment about what another student has said. Please don't continue to comment on a discussion that has been "solved".

Analog Inputs

Discussion:

We've investigated using the Arduino to read in a digital value. In this case, digital means that a quantity can only have one of two values, namely HIGH (synonymous with "1" or +5 V) or LOW (synonymous with "0" or ground).

Click through the break to begin this activity.

A Better Button

Components needed for this lab:

• push-button momentary switch
• (1) 1-k resistor
• (1) 10-k resistor
• several hook-up wires

Discussion:

• Use the diagram above to build the circuit with the button
• In this case, the 10-k resistor is called a "pull-down" resistor because it normally "pulls" pin 7 to ground. The default "reading" of pin 7 will be LOW since it is connected to ground.
• When the button is depressed, pin 7 is also connected to +5 volts. Since the button itself offers almost zero resistance, pin 7 is "closer" to 5 V than ground, and so it will read "HIGH". 
• Notice that when the button is depressed, the +5-volt rail is connected to the ground rail and current will flow between the two. That's why it is imperative to use a fairly large (in this case, a 10-k) resistor--we don't want too much current flowing in that branch of the circuit, overheating the button, and possibly burning out the pins of our Arduino!

Click through the break for more instructions... ...

Arduino Link

CC image licence BY-NC-SA 3.0

• Click here for the "S.O.S." code discussed in class.
• Click here for the "Let's Use a Switch!" code discussed in class.

Science Fair: 2013

Photo by Mars P.

Getting Started

The complete informational packet for the 16th Annual St. Clair County Science and Engineering Fair is now posted online.

1. There are three major project categories. What are they?
2. What are the maximum allowable dimensions for a high school science fair project's display?
3. What would be the proper way to cite a Times Herald newspaper article called "Great Lakes are Really Great"? The article was written by Joe Smith on January 17, 2013.
4.  Draw a rectangle on your page. If this rectangle represents a typical 3-sided display board, label the major components.
5. What is the difference between an independent variable and a dependent variable? Give an example of each for a hypothetical experiment.
6. What is an abstract? How long should it be?

Choosing a Project Type

One of the first choices to make when thinking about what you want to do with your project is deciding whether to do an engineering project or a science project. Use the Science Buddies' site to answer the following questions.

1. What are the steps of the typical "engineering design process"?
2. What steps are similar when comparing the "engineering design process" and the "scientific method"?

Choosing a Specific Project

Often, the hardest part about doing a science fair project is selecting a topic to study. It's best to choose a topic that interests you. Coming up with an original idea is nice, but sometimes we need a little inspiration.

1. Do a Google image search for winning science fair projects. Try to draw some quick generalizations... ... Are there any similarities among various winners (not in their subjects, but in their presentation or style)?
2. There are many resources online with science fair project ideas. Let's use the one featured at education.com. Browse through the list, read them, and write down at least three topics that you might find interesting. Make sure your choices are not the same as anyone else sitting near you in class (we want unique projects!).

Note about comments: comments have been disabled for this post because this is a specific outline we're following as an in-class assignment.

Looking Back at Semester One

Photo by Andrew Mccluskey used with Crative Commons license

Now that we've finished the first semester, I'd like to take a minute to look back and reflect. Often, teachers ask about what topics were the most interesting or fun to study, but I'd like to take a slightly different approach here.

What topic or topics from semester one did you find the most frustrating? Be clear in why you're choosing what you're choosing... ... was it frustrating because it was difficult? Not well explained? Boring? Something else? I'm curious to see if we notice any recurring ideas. Please post in the comments section!

Projectile Motion

This really cool simulation is courtesy of the PhET project at the University of Colorado. Play around with it until you get comfortable and familiar with the controls.

Answer these questions as comments. Don't answer identically to what someone else has already said--either add to his or her response, indicate that you disagree with the response, or answer a question that hasn't been already answered. Please only comment on 2 questions so everyone has a chance to get some points.

1. What is the range of a golf ball if it is launched at a 40° angle with a speed of 15 m/s?
2. What is the total time the golf ball from question (1) is in flight?
3. Neglecting air resistance, how does the launch speed affect the projectiles overall range?
4. Neglecting air resistance, how does the launch angle affect the projectiles overall range?
5. Neglecting air resistance, how does the projectile's mass affect the projectiles overall range?
6. Of the preset choices, which 3 objects appear to be most affected by air resistance? How do you know this?
7. Neglecting air resistance, what launch angle produces the maximum range for a projectile?
8. Taking air resistance into account, what launch angle produces the maximum range for a pumpkin launched at a speed of 10 m/s?