Physics: Discussion, Questions & Potential Solutions

[Joseph41]

This thread is for all exam-related discussion. Was it easy? Was it hard? What did you get for each question? Feel free to post any and all of your thoughts below.

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[Seno72]

Yeah, spring compression was prety hard, probably lost 2 marks. Also that power loss question in transformers question was pretty dodgy. Everything else was pretty good.

[KiNSKi01]

Yeah totally stuffed up second and third part of spring question

Think answers should have been 0 m/s^2 and 0.05 metres


One of the tranmission questions were dodgey but I think the main thing you had to recognise is that the power was the same as it was in the first scenario

[Seno72]

Yeah the answer for third part was 0.05 m. So stupid mistake. You can use kx = mg.

If the power was the same it would have been pretty easy. But I would have thought the power dissipated would be different from the original scenario. What did you choose for the definition for uncertainty in the multiple choice? I said it was the doubt in the measurement (choice A)?

[KiNSKi01]

Apparently since it says in the question that the globe still operates the same as it did before (lol something like that) power was the same.

Got the same answer for mcq 👍

[Nomi16]

Yeah totally stuffed up second and third part of spring question

Think answers should have been 0 m/s^2 and 0.05 metres


I reckon the answer for part b is 9.8 m/s^2 as that's the maximum acceleration due to gravity.

[jpulvirenti]

what did you get for the powerloss questions

[AlphaZero]

Same as yesterday.
We'll do our best to get the solutions out as quick as we can!

[KiNSKi01]

Yeah that’s what I had but it’s wrong

The question asked what is the acceleration when the ball had its max velocity

Once the ball comes into contact with the spring it is still acccelerating but the value for its acceleration decreases. Once the value of acceleration reaches 0 m/s^2 (when mg=kx) the ball reaches its max velocity

I’m guessing you did the same as me and assumed that as soon as the ball came into contact with the spring it would start slowing down. Unfortunately that’s not true Ahahah

[number6603]

I feel like, logically, it has to be 0 - if the acceleration is positive, then it hasn't hit its max velocity. If it's still accelerating, it's increasing velocity, and it can't be at maximum velocity if its velocity is still increasing.

[Theodric_Ironfist]

What about part a of the spring question? Says to show that k = 392. I used to mg=kx and got k=39.2. Possible typo?

[KiNSKi01]

Nah had to use energy equations

Mgh (top) = mgh (bottom +1/2kx^2 and solve for k

[aussiboi]

No vcaa are never wrong

mg∆h = 1/2kx^2
2 x 9.8 x 2.5 = 1/2 x k x 0.5^2

rearranging it to find k gives 392 xD

[Theodric_Ironfist]

No vcaa are never wrong

mg∆h = 1/2kx^2
2 x 9.8 x 2.5 = 1/2 x k x 0.5^2

rearranging it to find k gives 392 xD

But it says when they come to rest. Then the forces would be balanced and mg=kx. Unless they meant "momentarily" at rest, in which case they should have specified.

[aussiboi]

How did we meant to draw the 3 mark graph of emf idk i drew my like sin