SMART Energy presentation errors: questions embedded in the presentation: #42 answer should show GPE not EPE, #50 question is grammatically incorrect, #54 typo in answer-KE shouldn't be there.
Yuriy Zavorotniy • 4 years, 4 months ago
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Hi Jennifer,
The area under the curve of a force vs displacement graph is the work done. In this problem, the area under the graph (for the first 10 meters of displacement) forms a triangle with a base of 10 and a height of 20. As the area of a triangle is 0.5bh, the work done during the first 10 seconds is 100 J.
Sorry. This was on the presentation. I will let you know if this is also on the classwork as well as I am now working on the problems. Also, please check out the F=-kx graph on the PDF presentation from pages 74 to 79. The line was reversed probably by computer error. The line on the graph on the Smartboard presentation is accurate.
Joan, you actually unearthed a bigger problem. Question 41, which was where the spring constant was calculated was written wrong. The intent was that the same spring constant would be used for questions 42 and 43. Question 41 should've stated that a vertical spring was stretched by a hanging mass - then you're allowed to say mg = kx. Just because you stretch a spring in an arbitrary direction by a mass doesn't allow you to use mg = kx. All three questions have been rewritten and will be posted. The pdf version does have the graph's "backward." But all of them should've mentioned that the external force was being plotted and not the restoring force. That has also been corrected and will be reposted. Thank you very much! John
Melissa Axelsson • 1 year, 11 months ago
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Joan - the newly updated presentation is now posted. We were also able to correct the issue on the inverted lines in the PDF.
1) In the energy presentation Slide 122 implies that a 1 Watt = 1 Joule/second by talking about a 100 Watt bulb. That should be made explicit, as it defines the Watt as a unit of power. Probably a slide by itself.
2) A slide explaining the kilowatt-hour (KWH) as a unit of energy might be the most applicable part of this section to most students future lives. Better yet would be a slide explaining that when they pay for electricity, they will pay based on KW (size of the pipe) and on KWH (usage). This should also be in AP. I would be happy to help with this.
Matthew, these are great comments. As soon as school is over, we are starting a project to refresh the entire course - I would like to fold your comments into this process. Thanks very much, John
I teach in a district that starts on August 6th. Do you think the refresh of the course will be done by then? I am thinking about how to get my units planned out for next year school year. Thank you for these amazing resources! My students are learning and enjoying physics and passing their state end of course exams!
Our plan is to start Algebra Based Physics revision on June 26th. Based on our last physics meeting we are agreed to make some changes to only mechanics to reduce its volume. The remaining portion of this project will be to revise some of the presentations, homework/classwork sets and create "problem solving techniques" notebooks.
I can see that it can be done by the first week of August. Thank you. Yuriy
Matthew, We define Watt as the unit of power in the slide after the lightbulb slide. So, I will move the slide with the picture of Watt forward, and then have the lightbulb slide and talk about how it's rated to deliver 100 W if connected to household voltage (120 V). And I pay my electric bill by KWH (at least I think I do)- I'm not familiar with a charge for KW, unless that's some kind of fixed charge for the service - please clarify for me, thanks!
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