General Thoughts: Physics (2 Viewers)

[BillKyriakos]

Regarding that question about the trolley with the copper bar, what did everyone graph the velocity to be?

 

[malcolm21]

Regarding that question about the trolley with the copper bar, what did everyone graph the velocity to be?

had no idea, i just had velocity decreasing through b and c then it goes back up again but not as high as v

 

[astroman]

Regarding that question about the trolley with the copper bar, what did everyone graph the velocity to be?

increase then decrease?

 

[sy37]

had no idea, i just had velocity decreasing through b and c then it goes back up again but not as high as v

It doesn't decrease through B and C

If you measure the trolley with the A-B-C-D range you'll find both are exactly 3cm

It should start decreasing slightly before since the magnet isn't situated exactly at point B

and since the magnet will continue attracting after the front of the copper has slid through (i.e. the back of the copper bar) it should begin increasing just before D

 

[malcolm21]

increase then decrease?

wtf howd u get it increases? I wrote something about induced emf slowing it down

 

[HecticLad]

Regarding that question about the trolley with the copper bar, what did everyone graph the velocity to be?

mine was like a sideways cubic function tbh, idk tbh

 

[keepLooking]

wtf howd u get it increases? I wrote something about induced emf slowing it down

Eddy currents always speed the vehicle up. What are you talking about? /s

 

[Pab]

had no idea, i just had velocity decreasing through b and c then it goes back up again but not as high as v

This one confused me, was it just travelling at a constant v or was it sort of pushed with the initial velocity being v

 

[IamKirby]

How does the velocity increase? I thought induced current by Lenz's law would 'repel' the cart until it passed underneath at which point it would be attracted back? I had decrease the whole time, beginning to level out at D.


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[malcolm21]

Eddy currents always speed the vehicle up. What are you talking about? /s

fuck the law of conservation of energy yall

 

[HecticLad]

wtf howd u get it increases? I wrote something about induced emf slowing it down

it doesnt increase at all tbh, because it slows down approaching the field due to lenz law repulsing the cutting of magnetic flux, however once its in the field, the same thing will want to stop it from leaving

 

[p0llex]

Regarding that question about the trolley with the copper bar, what did everyone graph the velocity to be?

A lot of wrong answers here:

You needed to recognise that this is the same as electromagnetic braking. Magnets do not attract copper.
So essentially it decreases wherever its in the magnetic field, decreases the most a bit to the left of the magnet, and once it's out its velocity doesn't change.
At no point does the velocity increase.

 

[jackleung34]

inb4 b6 cut off 70

 

[mishconduct]

yeah doesn't it go down the whole time, i also accounted for a slight amount of friction so it is decreasing at different rates the whole time. lots of others didn't apparently but i explained it in the explanation and also started the line from v so it should be OK.

 

[keepLooking]

inb4 b6 cut off 70

I hope so. I probably got early 70's ;[

 

[p0llex]

mine was like a sideways cubic function tbh, idk tbh

Yep this is good, but to be very technical it will decrease more from A to B than from B to C because the rate of braking is proportional to the speed.
I don't know if they'll require that much detail though

 

[WillieHoang]

my answer is it slowing down from A to C, then from C to D it go back to initial velocity, anyone got the same?

 

[malcolm21]

just drew that copper question again, looks impeccable, mine looked like this, is it wrong?

(ignore the slight increases randomly using a mouse is hard)

 

[genodeg]

mine was like a sideways cubic function tbh, idk tbh

lol i did the same thing my whole graph was so bad... forgot pencil so theres a tiny scribble on it to top it all off RIP

 

[HecticLad]

Yep this is good, but to be very technical it will decrease more from A to B than from B to C because the rate of braking is proportional to the speed.
I don't know if they'll require that much detail though

yeah thats exactly what i was thinking, just cbf bothering to go into that much detail for 5 marks for a graph & justification