Apologia Physics: Newton's Laws

Newtons mini stations

More Newtons stations

Even more Newtons

Discussed Newton's laws of motion.  Did four easy demonstrations today to as examples.  These are easy and fun to do.

1)  Blow up a balloon then let go and measure how far the balloon flies.  It is difficult to get the balloon to fly straight so do several iterations.
Then blow the balloon up to the same size, add some weight, then let if fly and measure how far it goes.  For weight, attach some coins or popsicle sticks.  Putting the weight inside the balloon seemed to work better.
2)  Put and empty baby food jar or similar container upside down over another identical container.  Put an index card between the two.  Pull the card out fast enough that the top jar remains on the bottom jar.
3)  Put an index card on top of a baby food jar and put a large washer or a quarter in the center of the card.  Pull the card out quickly.  If you do it fast enough the quarter drops to the bottom of the jar.
4)  Stack up at least six or seven quarters or large washers.  Sharply hit the bottom quarter with a plastic ruler.  The bottom one or two quarters will go flying off but the remainder of the stack should just drop down with out scattering.

Which laws are being demonstrated here?

Each student is required to write a lab report on one of the above demos.  Each report should include:

Student's name
Date
Title of lab
Purpose of lab
Hypothesis
List of materials
Outcome of the lab
Discussion of results-what went right, what went wrong, what could be done to improve results
What you learned
Sections of the report should be written in paragraphs with proper punctuation, grammar, spelling, etc.  The English Comp lesson comes free with the Physics class!
Write in the third person, present tense, and active voice.


Here are a few photos.

Steps to Write a Lab Report (Mrs. Stevens' guide)

Last week, we did another lab, Elephant’s Toothpaste.  Now, the class should learn how to write a report and draw conclusions.  Lab design, creating hypotheses, and drawing conclusions are tedious to teach.  Here is the lab rubric I use for Chemistry.  Last week Elephant’s Toothpaste uses hydrogen peroxide, yeast, and dish soap.  The kids varied the number of grams of yeast and timed the soapy solution as it reached the top of the test tube.  Here goes the lesson.
1.  What is the hypothesis?  A hypothesis has two parts: null and alternate
   a. The null hypothesis for this lab is, “There is no relationship between the number of grams of yeast and the time it takes for the soapy solution to reach the top of the test tube—or The time of reaction is independent of the amount of yeast.”
   b.  The alternate or alternative hypothesis (your best guess) is, “The more grams of yeast, the shorter the time for the soapy solution to reach the top of the test tube—or The more yeast, the faster the reaction.”

2.  The next section is background material.  Yeast contains the enzyme, catalase, in the cell’s peroxisome  organelles.  Hydrogen peroxide is a common waste product in cells. (Waste is bad.). The catalase breaks down hydrogen peroxide.  In this lab, the yeast is allowed to bloom and produce catalase, which breaks down hydrogen peroxide.  Kids can write the background in quotes—but must cite the source.

3.  Next is the chemical reaction for this experiment., if pertinent.  Hydrogen peroxide breaks down in the presence of catalase into water and oxygen.  Students may write the balanced reaction neatly in pen or 2 H2O2 —— H2O + O2

4.  On to the materials.  The materials include the following items:  test tube rack, six test tubes, a test tube holder, scoopula, one disposable, graduated, transfer pipette, a 50 mL graduated cylinder, a 10
mL graduated cylinder, cell phone stop watch, three plastic beakers, one digital thermometer, a tray or trough for overflow, a digital scale, one weigh boat, 20 grams of yeast, 30 mL dish soap, 200 mL water, and one craft stir stick.  Note the grammar!  Numbers ten or fewer are spelled and greater are written in Arabic character, one and 50.  Please note a colon follows a noun.  The sentence above is an example of the use of third person, present tense, active voice, and indicative mood.

5.  The next section, results, includes the data, ideally a table or chart.  The student may write the results.  For example, the results are five grams of yeast produces suds in 4.9 seconds.

6.  The procedures must be discussed step by step.  The controlled variables are the water temperature, the amount of water, dish soap, and hydrogen peroxide.  The independent variable is the number of grams of yeast.  The student completes three trials.  For each trial, the student adds one milliliter of yeast solution to one milliliter of dish soap and five milliliters of hydrogen peroxide in a 25 mL test tube.  The student measures each trial with a stopwatch to assess the time the soapy solution travels to the top of the test tube.  The student records each trial in a table.


7.  The discussion section follows the data.  This section has any observations or mistakes.  The student notes that 25 grams of yeast causes an eruption of suds to quick to measure.  This is the point
the student determines if the results support or refute the null or alternate hypotheses.  It is not
unusual for the results to refute both.  Here, the child should use the Claim Evidence Reasoning approach to describe the results.  The claim is that more yeast results in a faster reaction.  The student’s data table should indicate shorter intervals.  The reasoning is that more yeast produces more catalase, consequently breaks down more hydrogen peroxide.

8.  Lastly is the conclusion.  My standard conclusion is this one, “More trials are indicated.”  “More study is needed to determine the results support the alternate hypothesis.”

Apologia Physics Two Dimensional Motion Conclusion

Summarized main points of parabolic motion and discovered a few things:

When a projectile is fired or thrown near the surface of the earth its path is parabolic.  Several students debated the pronunciation of the noun, parabola, and the adjective, parabolic.

The x and y components of a projectile's motion can be treated as two separate one-dimensional situations.  The x component's velocity does not change once the projectile has been launched.  The y component is gravity.

A projectile's maximum height will be reached when the y component of its velocity is zero.

If the projectile lands at the same height from which it was launched, it will reach its maximum height at the midpoint of the journey.   The final value of Vy will be the negative of the initial value of Vy.  In other words, the final velocity equals the initial velocity.  Good examples are throwing a football to anther person, firing a cannon at a target.

To show that the y component velocity is independent of the x component we timed how long it took a rubber band to hit the floor after being shot a few feet as shown below and also by just dropping it from the same height.  Two groups had times within a ten percent error, very good, and one group was repeatedly off by 30%  I should have had them change timers!

In calculations remember that the Cosine of zero is 1 (one) and the Sine of zero is zero.

We looked at the range formula.  Range = V^2 (initial velocity) times sin2times the angle divided by gravity.  It is not important to be able to derive this formula although the derivation is in the book.  You would use this formula to determine how far a projectile would fly based on initial velocity and the angle from the ground. 

We made several observations from the range formula.  If you double the initial velocity, the range is quadrupled as V is squared in the range equation.  If you were aiming at a target and your first shot fell short, you would decrease the angle to get the projectile to go farther.  Handy to know if you are firing a mortar or throwing a football.