Exam Discussion!

[shroomer101]

What did you guys get for the '' eV question?

I think I got 8.9 ev

[speedy]

The halfway point is when the speed will be a maximum, yes, but the extension found from an earlier part is 0.8m. The value you found IS the extension as you are calculating from the unstretched length, so the 0.4m length of the unstretched spring doesn't apply.
Then the halfway point will be at x = 0.4m and you use conservation of energy principles

Uhh, you sure? Because I'm pretty sure it oscillates between 0.4 and 0.8?

[sani8274]

Meterial n strctures
A
B
B
D
A
B
B
A
B
A
C

[Sono69]

I think I got 8.9 ev

Same here, also got 625 ohms for that resistor question

[KayKay]

Could you determine the mass of the planet?

You couldn't because according to Kepler's Law: T^2/R^3=4pi^2/GM all objects at that radii will orbit the sun in the same time period, given the mass of the Sun, no matter what the mass is. So from that info, the mass could be anything.

[shroomer101]

Uhh, you sure? Because I'm pretty sure it oscillates between 0.4 and 0.8?

The x found which is 0.8 is the length of extension so it oscillates from 0.4 to 1.2m

[Bronzebottom64]

Meterial n strctures
A
B
B
D
A
B
B
A
B
A
C

I don't think the last question was c. I originally thought this too but if the inside three were all cables then the outer two would fall down. As such I put A.

[SeanC]

yeah i got 8.9eV also

[S61778]

You couldn't because according to Kepler's Law: T^2/R^3=4pi^2/GM all objects at that radii will orbit the sun in the same time period, given the mass of the Sun, no matter what the mass is. So from that info, the mass could be anything.

It was 2 marks, so would saying 'no' be 1 mark? I did that questions at the very end and just said no, didn't have time to explain

[NathanGauci]

yes i got 26V as well

I treated the circuit as a voltage divider and got that. So relieved

[KayKay]

It was 2 marks, so would saying 'no' be 1 mark? I did that questions at the very end and just said no, didn't have time to explain

Yeah saying no will give you 1/2 I think

[3fold]

I got 625 for the resistor too.

[theshunpo]

Same here, also got 625 ohms for that resistor question

Sounds good to me!

[Sono69]

Anyone do the sound detailed study and remember what they got for the resonance questions?

[S61778]

Yeah saying no will give you 1/2 I think

Also for the max speed of mass spring question, I got 2m/s but I think my working out was wrong. I did elastic potential energy is converted to kinetic energy.

So from the previous question, I got x=0.4m
Then, calculated the Spring potential energy with 1/2kx2
Then made that equal to kinetic energy and solved for v
Got v=2m/s
No marks or?