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Mod 5 – Advanced Mechanics

Hi again! I hope you’ve had a restful break and that lockdown hasn’t been too crazy! In this article I’ll try to breakdown some guidance for preparing for Mod 5: Advanced Mechanics.

Firstly, here’s an interesting thought:

It is more worthwhile doing one practice paper twice, than doing two practice papers once.

Okay, to get to the crux of it: do not do the entire practice paper again. Doing the practice paper twice means, the second time round, only doing the questions you made mistakes on. This is far superior to doing two practice papers only once! By doing a practice paper again (and only the questions you did not get full marks in), you start to become aware of why and how you got things wrong, or did not quite meet the mark.

You actually start to improve.

Doing two practice papers once is better than nothing. However, if you do not properly review those practice papers and understand why you made errors, there is little learning to be done. You are not as likely to improve and build on your past mistakes, without properly attempting those wrong questions again. Hence, the sage adage.

Now, on to Mod 5.

Significant Figures

Your final answer should have significant figures to the least number of sig figs that have been provided in the question (or used in calculation). For example, if a question on finding the force from the Motor Effect gives I = 3.0 A, B = 0.0426 T, and l = 3.00 m, your answer should have two significant figures. Although B and l have three sig figs, the current is only 3.0 A, which is two significant figures. Also, if you use 9.8 for gravity from the reference sheet, that’s two sig figs! So, your answer (if you use 9.8 in your calculations) should be two sig figs too.

It is important to make sure every question has proper sig figs!


In Mod 5, calculations are everywhere. It’s very easy to mistake a plus for a minus sign, and if you have handwriting that is not so good (like mine), then sometimes a nine could be interpreted as a four. To avoid these errors:

- Write clearly, and in steps.

- Define a positive and negative direction (labelling with an arrow with a small + on it).

- Make sure gravity always acts downward.

- Use the calculator frequently and accurately.

- Break long calculations down into parts.

One of the silliest mistakes you could make in a question is simply typing something wrong in the calculator. It is important to write things down as you go: small scraps of paper where you put numbers, bits of calculation, things you can come back to and not forget them.

Also, if you’re interested, there’s the ‘store’ feature on some calculators that may make it easier to instantly type G (6.67 x 10^-11) and M (6.0 x 10^24).

Steps are so important in Mod 5 calculation questions. The markers want to see the following structure:

1. Identify the appropriate formula. (write the formula down!)

2. Identify the values required.

3. Substitute the appropriate values. (from the question!)

4. Solve correctly.

While it looks easy, silly mistakes are such a trap. They’re annoying, and your job is to try to remove them as best you can.

Check Your Work

If you finish the paper early, check those calculations. Wipe your brain of any prior memory that you used to do that question, and do it all over again. With a fresh mind, you can check your working and calculations without a biased perspective. One of the biggest struggles in a Physics exam is overcoming confirmation bias, where you believe you are right and so avoid questioning your own methods used in the problem.

Clear your mind, and do it again.

That’s all from me this week. Mod 6 next week – Lenz’s Law! Work hard, but don’t forget to rest. 😊


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