Year 12 Physics
Week Beg 18th May
Last week of the materials topic. We have covered most of the basics, stress/ strain/ youngs modulus/ energy stored/ Hookes law so please ensure that you have understood all of that. As I keep emphasising its usually the maths of the conversions that cause the most issues and that certainly was the case with the questions I set. You get the right answer but the wrong power of ten. Does it give the diameter or the radius or the area. If you look at the answers I sent out yesterday I believe my last answer was wrong because I looked at both wires instead of one. Its little mistakes like that. Most peoples significant figures were pretty good. No silly answers 7 decimals long or reoccurring dots above numbers (ok for maths but not Physics)
The last section 11.4 p192 looks a bit more at what happens when you stretch different materials, especially if you exceed the elastic limit. Figure one shows load extension graphs (not stress/ strain) for 3 materials. The idea being tht we doing a stretching experiment and measure the extension by not only increasing the load but then decreasing it and seeing if that makes a difference. The one for rubber is sometimes called a hysteresis curve. Its as though its storing energy as the force decreases.
We can see that the area under this graph is called the strain energy (and yet again we might be asked to calculate this energy by counting squares (not through trapeziums!) figure 2 explains this quite well. Notice that yet again the load/ force is on the y axis.
The stuff in the green box explains why plastic and rubber deform like they do. Worth reading but not a requirement of the course.
There is another formula at the top of page 193 but we have come across this before.
Read the work. Make a few notes (sketch the graphs) and attempt the questions.
Ive attached a multi choice quiz answers please by Thursday, no photographs please just the letters in an email! Don’t print it out.
Ive also set a Kahoot - no giving the code to someone else. Deadline on this is Thursday 22nd May 11pm
Mr Ellis will be emailing work to students.