Okay dokey, thanks for this. Q20 needs discussing on a few levels. a) It contains ideas from rotation which is STRICTLY not in the syllabus. b) Length contraction? AT A POINT? Since when does a point contract. More on this later. Q20 should be tricky, but should not contain ideas from outside the syllabus AND suggest that a a point can experience" length contraction". This question just wasn't checked properly in terms of examining if it is is the syllabus and should never have gotten past the important step of whether or not the PHYSICS is correct. Students are NOT taught that the instantaneous velocity of a tyre is zero at point of contact- certainly not in this syllabus,( although I suspect that many will be taught this nest year in response to a situation where the exam sets the syllabus). That a rolling wheel ( and I note the examiner was smart enough to include no slipping - its a pity they didn't check that the content was examinable, however) is the combination of a CW SPINNING wheel - (YES THIS IS ON THE SYLLABUS, as this is just regular ucm) - and a TRANSLATION of the wheel to the right. Combining both the liner translational velocity PLUS the tangential velocity of the points P Q and R of course allows this not known fact for year 12 physics students to be easily shown. ie the velocity of a tyre, wheel etc is zero at pt of contact, equal to v at the centre of mass and 2v at the top of the wheel. This is not intuitive and is not part of the current physics syllabus since the rotation elective was removed in 2001. Either the examiner believes that students can discover this in an exam situation - INCORRECT and simply poor passement OR They believed it is a legitimate question to ask based on the syllabus - INCORRECT. As evidenced by your statement, with no explanation, that the "wheel is not moving at P". Your velocity vector for point R ( upwards!!!) was also unconvincing. Its tangential ie towards the right and should be twice the length of the labelled vector of 0.4 c b) Although you alluded to the idea of a point, it is just embarrassing that the question was asked at all. What would our mathematical friends think? Points cant change in length because they have no length. Good exam MC questions are hard to set, and by and large NESA sets some outstandingly good questions over the years,, clever thoughtful and which can also produce good discourse amongst physics teachers. This is not one of these questions. You also do a fantastic job of providing excellent suggestions in how to answer these questions. So thank you for all of your fantastic work. On this occasion, I was disappointed. If you are independent from NESA why don't you call them out occasionally when they write such awful questions? In terms of the physics involved and the ineptitude in asking questions which ought not to be examined from a prescribed syllabus perspective, I'm afraid this question is indefensible.
I tend to agree with you. The other issue is that one cannot “see” length contraction and so the whole premise of seeing different lengths is erroneous. Having said that my video is not to call out NESA. It’s meant for students and occasionally poor questions get through and so students should be able to reason out the best response. So I provide guidelines on how to answer with the syllabus knowledge they have
@@PhysicsHigh Thanks for your reply, and taking the time to do this. You are a Physics teacher in NSW?.... so you absolutely have the right, and given your platform, the responsibility to call out an incorrect question. Maybe, maybe not. Very few students would be able to reason for the physics behind the different velocities; the best students would be torn over the erroneous concept of length contraction of a point. Thanks again
ERRATA: for Q13 (at 5:07) and q20 the answer is B (which I say), but due to an editing error I circled D in both cases.
Apologies
Thanks Paul, our exam was a gift tbh
FUCK 2022 WAS SO EASY, I HAVE my HSC physics tomorrow, im praying it goes like yours fuck me im stressed out right now.
@@Boomer1665It didn’t go the same as theirs
@@Boomer1665 and fastforward a year later i have the exam tmrw as well LMAO
Okay dokey, thanks for this.
Q20 needs discussing on a few levels. a) It contains ideas from rotation which is STRICTLY not in the syllabus.
b) Length contraction? AT A POINT? Since when does a point contract. More on this later.
Q20 should be tricky, but should not contain ideas from outside the syllabus AND suggest that a a point can experience" length contraction". This question just wasn't checked properly in terms of examining if it is is the syllabus and should never have gotten past the important step of whether or not the PHYSICS is correct.
Students are NOT taught that the instantaneous velocity of a tyre is zero at point of contact- certainly not in this syllabus,( although I suspect that many will be taught this nest year in response to a situation where the exam sets the syllabus).
That a rolling wheel ( and I note the examiner was smart enough to include no slipping - its a pity they didn't check that the content was examinable, however) is the combination of a CW SPINNING wheel - (YES THIS IS ON THE SYLLABUS, as this is just regular ucm) - and a TRANSLATION of the wheel to the right. Combining both the liner translational velocity PLUS the tangential velocity of the points P Q and R of course allows this not known fact for year 12 physics students to be easily shown. ie the velocity of a tyre, wheel etc is zero at pt of contact, equal to v at the centre of mass and 2v at the top of the wheel. This is not intuitive and is not part of the current physics syllabus since the rotation elective was removed in 2001.
Either the examiner believes that students can discover this in an exam situation - INCORRECT and simply poor passement
OR
They believed it is a legitimate question to ask based on the syllabus - INCORRECT. As evidenced by your statement, with no explanation, that the "wheel is not moving at P".
Your velocity vector for point R ( upwards!!!) was also unconvincing. Its tangential ie towards the right and should be twice the length of the labelled vector of 0.4 c
b) Although you alluded to the idea of a point, it is just embarrassing that the question was asked at all. What would our mathematical friends think? Points cant change in length because they have no length.
Good exam MC questions are hard to set, and by and large NESA sets some outstandingly good questions over the years,, clever thoughtful and which can also produce good discourse amongst physics teachers. This is not one of these questions.
You also do a fantastic job of providing excellent suggestions in how to answer these questions. So thank you for all of your fantastic work. On this occasion, I was disappointed.
If you are independent from NESA why don't you call them out occasionally when they write such awful questions? In terms of the physics involved and the ineptitude in asking questions which ought not to be examined from a prescribed syllabus perspective, I'm afraid this question is indefensible.
I tend to agree with you. The other issue is that one cannot “see” length contraction and so the whole premise of seeing different lengths is erroneous.
Having said that my video is not to call out NESA. It’s meant for students and occasionally poor questions get through and so students should be able to reason out the best response. So I provide guidelines on how to answer with the syllabus knowledge they have
@@PhysicsHigh Thanks for your reply, and taking the time to do this.
You are a Physics teacher in NSW?.... so you absolutely have the right, and given your platform, the responsibility to call out an incorrect question. Maybe, maybe not.
Very few students would be able to reason for the physics behind the different velocities; the best students would be torn over the erroneous concept of length contraction of a point.
Thanks again
Thanks mate you're a legned.
hey mate, big mistake at 5:20. You circled the wrong answer as correct.
thought so, trying to memorise my answers :< Anxiety just shot way up
Bugger. Thanks. I’ll add an errata and comment which I’ll pin. It’s an editing error as I actually don’t see the picture whilst I’m filming.
@@zoom3993 sorry
#13
Thanks. Errata added.
#20
Thanks. Errata added in description and pinned.