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Saturday, January 31, 2009

Grade 11 Physics

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9 comments:

Anonymous
said...

Where can I find the outline for the labs/description on how to write a lab report (for assignments due Friday.)

i am not sure if this is to be used for posting this sort of problem, but i have used it for such purpose hoping that it may lead to a solution.

In the Snell's Law lab, for "part b" of the analysis section, you had told us on previous occasion of an error that a large portion of the class had demonstrated in their formative drafts. I shared this common error. It was that, from my calculations, the average index of refraction was significantly under 1.00 and that my experimental error was more then half.

I understand that these numbers are theoretically incorrect from your explanation of these problems in our labs. Unfortunately I haven't been able to find what calculations i might have done wrong to receive these numbers and I can't recall what you explained to be the method of solving this problem nor can i interpret the solution from the notes i took from your explanation.

you informed me to divide 1, by my measure average index of refraction. i have done so and do not understand where this number is to lead me and do not no how to change my experimental error from being "too high".

These are common problems i have been trying to solve for some time now and have gained no ground upon. I hope you may be able to give some sort of, if at least, a hint as to where i may direct my calculation attempts so that i may eventually arrive at a preferred answer.

I understand it is somewhat late of me to be asking of such help, but it seems as though these problems never arise until realized, and never realized until attempted. Unfortunately the procrastinating of the action of attempting has been the major flaw in this course of action.

Any help offered would be greatly appreciated! :)

P.S. Also which values do we use for index of refraction when measuring critical angle? The experimental, or accepted values?

Hi, The problem that many people encountered was realizing that the incident medium is different in part B than it is in part A. In part B the incident medium is the acrylic, and the refraction medium is the air. When sin theta 1/sin theta 2 is calculated that is giving us the value for n2/n1 (rearrange snell's law to find that formula). In part A since n1 is air, the fraction turns into the value for n2. In part B since n2 is air, you actually calculated 1/n1 (the inverse of the index of refraction for acrylic) you probably calculated it to be 0.67...so 1/0.67 is approximately 1.5

For the critical angle, you will probably have measured it during your experiment... you can compare that value to the calculated one using the accepted value for acrylic.

You are right...you should be asking this kind of question much earlier. There was a help session at lunch that was poorly attended. That would be the best time and place to ask for lab clarification.

Hello Walker I'm not sure what you mean by friction lab....

Tomorrow you need to hand in a final copy of an optics lab.

Tuesday after the break you need to hand in part A and B of the cart lab that we did with the computer sensors. Read the sheet for the requirements of the lab.

im completely lost on the cart lab. i dont understand the experiment we are supposed to create, and im lost with calculating the velocity because you said to find tangeants as opposed to just using an equation.

Part A is separate. You need to design an experiment, but you don't have to do it. Tell me what you would do, and what you would use, and what you would measure.

Part B was with the cart. You will have data for position and time. Draw the d-t graph. To find the velocity at any instant, draw a tangent to the d-t curve of best fit at the instant in question. The slope of the tangent is what gives you the velocity.

Follow what is asked on the handout. I look forward to seeing your analysis and lab work tomorrow.

P.S. I was there at lunch and after school today answering questions.

## 9 comments:

Where can I find the outline for the labs/description on how to write a lab report (for assignments due Friday.)

The lab is based on the one in the text book (find the one with the light bulb and meter stick)

The lab report guidelines were handed out in class before the first lab that we did. They can also be found on my website here

Ask me in class tomorrow if you still need help. I believe there are extra copies in the Model Notebook kept by our peer tutor.

i am not sure if this is to be used for posting this sort of problem, but i have used it for such purpose hoping that it may lead to a solution.

In the Snell's Law lab, for "part b" of the analysis section, you had told us on previous occasion of an error that a large portion of the class had demonstrated in their formative drafts. I shared this common error. It was that, from my calculations, the average index of refraction was significantly under 1.00 and that my experimental error was more then half.

I understand that these numbers are theoretically incorrect from your explanation of these problems in our labs. Unfortunately I haven't been able to find what calculations i might have done wrong to receive these numbers and I can't recall what you explained to be the method of solving this problem nor can i interpret the solution from the notes i took from your explanation.

you informed me to divide 1, by my measure average index of refraction. i have done so and do not understand where this number is to lead me and do not no how to change my experimental error from being "too high".

These are common problems i have been trying to solve for some time now and have gained no ground upon. I hope you may be able to give some sort of, if at least, a hint as to where i may direct my calculation attempts so that i may eventually arrive at a preferred answer.

I understand it is somewhat late of me to be asking of such help, but it seems as though these problems never arise until realized, and never realized until attempted. Unfortunately the procrastinating of the action of attempting has been the major flaw in this course of action.

Any help offered would be greatly appreciated! :)

P.S. Also which values do we use for index of refraction when measuring critical angle? The experimental, or accepted values?

Hi,

The problem that many people encountered was realizing that the incident medium is different in part B than it is in part A. In part B the incident medium is the acrylic, and the refraction medium is the air. When sin theta 1/sin theta 2 is calculated that is giving us the value for n2/n1 (rearrange snell's law to find that formula). In part A since n1 is air, the fraction turns into the value for n2. In part B since n2 is air, you actually calculated 1/n1 (the inverse of the index of refraction for acrylic) you probably calculated it to be 0.67...so 1/0.67 is approximately 1.5

For the critical angle, you will probably have measured it during your experiment...

you can compare that value to the calculated one using the accepted value for acrylic.

You are right...you should be asking this kind of question much earlier. There was a help session at lunch that was poorly attended. That would be the best time and place to ask for lab clarification.

See you tomorrow with you lab!

when is the friction lab due? is it only the final copy lab due tmrw?

Hello Walker

I'm not sure what you mean by friction lab....

Tomorrow you need to hand in a final copy of an optics lab.

Tuesday after the break you need to hand in part A and B of the cart lab that we did with the computer sensors. Read the sheet for the requirements of the lab.

awesome. thats all i needed to know, i was thinking they were both due tmrw, and i have a chem test first and havent begun on the friction lab...

im completely lost on the cart lab. i dont understand the experiment we are supposed to create, and im lost with calculating the velocity because you said to find tangeants as opposed to just using an equation.

Part A is separate. You need to design an experiment, but you don't have to do it. Tell me what you would do, and what you would use, and what you would measure.

Part B was with the cart. You will have data for position and time. Draw the d-t graph. To find the velocity at any instant, draw a tangent to the d-t curve of best fit at the instant in question. The slope of the tangent is what gives you the velocity.

Follow what is asked on the handout. I look forward to seeing your analysis and lab work tomorrow.

P.S. I was there at lunch and after school today answering questions.

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