• QCE

  • Urgent External Exam Questions

Howdyyy.

I'm struggling to differentiate for Question 19, on the 2020 external exam, Paper 1 tech free. Could anyone please show me a step-by-step working out because I tried it and I got confused. The marking scheme isn't too clear either.

This is the question book: https://www.qcaa.qld.edu.au/downloads/senior-qce/mathematics/snr_maths_methods_20_ea_p1_question_response.pdf (Page 16/24)

Answer scheme: https://www.qcaa.qld.edu.au/downloads/senior-qce/mathematics/snr_maths_methods_20_ea_mark_guide_pub.pdf (Page 10/24)

Edit: I'm also having trouble with Q20, like where did the -(5/pi) come from, in front of the cos?
-jinx_58

    jinx_58
    Hey jinx_58,

    I have written out step-by-step the differentiation of the function so I didn't finish the actual question off so here it is (sorry for my bad handwriting): https://imgur.com/a/zCIX360.

    As for question 20, the -(5/pi) comes there because when the integrated cos function is differentiated, the pi/5 will come out from inside the bracket to the front. So, in order to "remove" that, you must put -(5/pi). If that doesn't make sense, try differentiating that cos function and you'll see that it'll become the sin function because the -(5/pi) x pi/5 becomes 1.

    Hope that helped and let me know if you have any other questions (or you can't read my handwriting πŸ˜…).

    • PP

        PhytoPlankton
        Thank you! That really helped lol. I did the quotient rule for both functions and it messed me up, I forgot I could take out the k haha. And for the -5/pi, I had integrated wrong.

        -jinx_58

          Howdy again.

          I need help on how to do Question 6 and 9 on the tech active exam, 2021. Its multiple choice and I don't know how to do it on my calculator (TI 84 Plus CE).

          Marking guide:
          https://www.qcaa.qld.edu.au/downloads/senior-qce/mathematics/snr_maths_methods_21_ea_mark_guide_pub.pdf

          Question booklet: https://www.qcaa.qld.edu.au/downloads/senior-qce/mathematics/snr_maths_methods_21_ea_p2_mc_question.pdf

          I'm also having trouble doing Question 9 on the tech-free paper for multiple choice:
          Marking guide: same as above
          Question booklet: https://www.qcaa.qld.edu.au/downloads/senior-qce/mathematics/snr_maths_methods_21_ea_p1_mc_question.pdf

          Thank you,
          -jinx_58

            jinx_58
            Hey jinx_58 again,

            I used a different graphics calculator to you when I did it so I wouldn't be able to tell you the specific buttons but you should be able to get that info off your calculator manual or online. With a scientific calculator all you have to do for question 6 is 8C6(0.86)(0.22) + 8C7(0.87)(0.21) + 8C8(0.87)(0.20) which should give around 0.797.
            As for question 9, for our graphic calculator, we just went to the graphing function then graphed both of those functions then we had an option to find the intercept of it so it was easy as that. Worst-case scenario, you use the graphics calculator to equate both functions and solve for x.

            Hope that helped.

            • PP

              Thank you PP, again, I really appreciate your help 😁

              Hi, Me again. For the third time. Damn I feel unprepared for tomorrow. πŸ˜…

              Could someone please explain the answer to question 13c on the 2020 external Paper 2? Like in simple terms please, because I get the first part but not the second part.

              Question paper: https://www.qcaa.qld.edu.au/downloads/senior-qce/mathematics/snr_maths_methods_20_ea_p2_question_response.pdf

              Marking guide: https://www.qcaa.qld.edu.au/downloads/senior-qce/mathematics/snr_maths_methods_20_ea_mark_guide_pub.pdf

              Edit: How do I know when to use the binomial probability distribution function on my calculator vs. the binomial cumulative distribution function? What words do I look for in the question?

              Thanks again.
              -jinx_58

              13 days later

              Howdy! Could someone please help me out with this question:

              The period of revolution of the planet Saturn around the Sun is 30 times that of Earth. Determine how many times further Saturn is from the Sun than Earth.
              A) 3.1
              B) 5.5
              C) 9.7
              D) 30

              The answer is C but I have not clue how they got there. The marking scheme stated the T2/r3 = 4pi2/GM formula.

              -jinx_58

                jinx_58
                Hey jinx_58,

                The marking scheme is somewhat right in using T2/r3 = 4pi2/GM because I think it uses Kepler's third law which is the ratio T2/r3 = T2/r3. To start, I am going to let:

                • TE = period of revolution (PoR) of Earth
                • TS = PoR of Saturn
                • rE = radius of Earth
                • rS = radius of Saturn

                Thus, the ratio is: TE2/rE3 = TS2/rS3. So assume the PoR of Earth is 1. So, the ratio is: 12/rE3=302/rS3 (because PoR of Saturn is 30 times of Earth). Rearranging that,
                rS3/rE3=302/12
                rS3/rE3=900
                rS/rE = βˆ›900=9.65=9.7

                Hope that helped. Feel free to ask any more questions.

                • PP

                  For VCE we get to take in an A3 notes page - idk about u guys interstate tho.

                  Would strongly suggest putting the rearranged formulas down if you can. SAVES SO MUCH TIME.

                    God
                    Hey God,

                    Unfortunately I wasn't allowed to take in anything except for writing utensils, a water bottle and a calculator, according to QCAA and I believe they haven't changed that rule for this year. But I really wish we could do that.

                    • PP

                        God
                        Yeah, we get a formula sheet, but if we don't know how to use the formulas, we're screwed. And the formula sheet is clean and given to us with our exam paper. And it still hasn't changed from what @PhytoPlankton experienced. We can take in a clear plastic water bottle, QCAA-approved calculator and 2B pencils, blue and black pens. No whiteout or rub-out pens.

                        It'd be pretty awesome if we did have an A3 page of notes though. But yet again, Queensland is quite new to the whole ATAR situation.

                        -jinx_58

                          Yikes. That’s a lot painful algebra

                            God
                            Unless we use numeric solver on our Graphics calcs

                            -jinx_58

                              jinx_58
                              Hey jinx_58,

                              For the blackbody radiation question, you just use Wien's displacement formula which is Ξ»max=b/T (where b=2.898x10-3). So, the answer should be T=257600K (I could be wrong tho).

                              As for stopping voltage, I don't think you actually need to know that for U3&4 (hence, why its not seen in the syllabus) but I believe you would use this formula: eV0= hc/Ξ» - W to work it out.

                              Hope that helped.

                              • PP

                                  PhytoPlankton
                                  Thank you PhytoPlankton.

                                  However, for question 8, the QCAA answers state it was Answer C, 190m. But for paper 2, QCAA has the wrong numbers subbed in for Question 9 so it could be a QCAA mistake.

                                  Thanks again,
                                  -jinx_58