Monday, January 17, 2011

We started today's class by going over last week's homework, Transparency 25-1 and Electromagnetic Induction.

For Transparency 25-1 Worksheet, the answers are:
1. Electrical energy; battery
2. Rod with a wire coiled around it; magnetic force created by the field magnet
3. N and S poles will reverse
4. Mechanical energy from the crank
5. Electromagnetic induction as the wire moves through the magnetic field
6. EMF increases

For Electromagnetic Induction, the answers are:
1) 0.97 V
2) 1.9 x 10^-3 V
3) 0.020 V
4) 1.0 x 10^-4 V
5) 3.74 V
6) 50 turns
7) 1.8 V

Later on in the class, we also went over Lenz's Law on the Chapter 25 Study Guide. The answers for this are:
- direction
- flux
- current
- armature
- increases
- back-EMF
- decreases
- decreases

Lastly, we received a couple of handouts; Induced EMF/Factors Affecting Induced EMF, a graph of induced potential difference vs time, Lenz's Law, a worksheet to practice Lenz's law and Transparency 25-2.

Please have the worksheet for Lenz's law and Transparency 25-2 done for homework.

-- Rainer

Wednesday, December 1, 2010

In today's class, we first went over the worksheets COULOMB'S LAW (the one where you had to underline the right answer) and ELECTRICAL FORCES.

For COULOMB'S LAW the answers are:
1-b. attraction
1-c. greater, less, 1/4 as much
2-a. doubled
2-b. quadrupled
2-c. quadrupled
2-d. 16 times

For ELECTRICAL FORCES the answers are:
1. -3.6 x 10^10 N (use Fe=kq1q2/R^2)
2-a. 7.80 x 10^-47 N (use Fg=GMm/R^2)
2-b. 8.80 x 10^-8 N (use Fe=kq1q2/R^2)
3. 2.5 x 10^19 electrons (use charge/e)
4. -1.76 x 10^8 C (use given mass/mass of electron)
5-a. 1.76 x 10^-15 N (add the force of each charged objects)
5-b. 2.63 x 10^11 m/s^2 (use a=Fnet/m)

Next we read through our first handout Coulomb's Law in One Dimension, Two Dimensions: Equilateral Triangle, and Two Dimensions: The Square.

To solve problems in one dimension, simply add the charges (like vectors). Don't forget that like charges repel and unlike charges attract.

To solve problems in two dimensions, first find the x and y components of each charge and add them together. Then combine the totaled x and y components by using the pythagorean theorem.

** Like vectors, electrical forces have direction.

Lastly, we were given question 5 on page 420 and questions 15, 16 and 19 on page 423 of the green books for homework!

Tuesday - October 26

In today's physics class, we went over Transparency 6-3 Worksheet (Uniform Circular Motion) , and both sides of the Centripetal Acceleration and Centripetal Force worksheet. Just a reminder, we had to hand in questions 4 and 5 of Centripetal Force worksheet for marks!

We also had to pick up one worksheet (Acceleration and Circular Motion) and two readings (Centripetal and Centrifugal Forces, and Motion Near the Earth's Surface). Please have the worksheet done for tomorrow's class and also read through both readings.

Also, if you still have your lab from Thursday, it is now overdue!

Enjoy the rest of your night!
-- Rainer

Friday - October 1

Friday's physics class was basically a chance for those who missed the momentum lab on Thursday to do and finish the lab.

For those of us who were in class on Thursday, our task was to finish and hand in the lab.

So, reminder to those who didn't finish or forgot to hand in their lab, it is now over due!!



Next thing on our to do list was to check the answers from Wednesday's questions from the duck book.

Basically, to find the momentum from a given force vs. time graph, we find the area under the given line.

If the line creates a triangle, its area can be found using the equation area = (1/5)(base)(height).

If the line creates a rectangle, its area can be found using the equation area = (base)(height).

If the line creates an irregular shape, simply cut up the shape into pieces of triangles and/or rectangles and find each area using the equations from above. (Don't forget to add up all the areas in the end).


The rest of the class should have been spent on doing questions 1 - 4 of the Impulse and Momentum worksheet.

If you did not get a chance to finish it in class, please do it for homework!



Enjoy the rest of your weekend!!!
-- RAINER