multiple choice (2 Viewers)

[pussy_cat]

i basically tried to ignore the diagram cuz it confused me, i just remembered my notes about electromagnetic braking and eddy currents, and the induction cooktop uses the same principle but except uses it to create heat, so i got d, what bout ppl who didnt get d?

 

[sub]

can somebody explain why can't q 11 can't be d?

i dont think they can, cos it IS d...but i would like to hear reasons for it not being d, incase i missed something

 

[L45er]

can somebody explain why can't q 11 can't be d?

I believe it's an ambiguous question. Both c and d involve eddy currents and the conservation of energy etc. But i think c is more correct as it is used to create motion etc like the brake stops motion... But as i said its quite ambiguous

 

[sub]

right...well, i take back my previous comment.

also, for q6, i put b...but apparently u can argue a, cos u get constant acceleration if a= 0 aswell right? so wouldn't that work too?

 

[gordo]

shiT! i put d for q6 but now i see that its b
this is how i worked it out but it might be wrong
the vehicle is accelerating uniformly horizontally, say at an acceleration of 9.8m/s2, the same as gravity
the ball is also accelerating at 9.8 m/s2 downwards, so if you compare these two components, you'll get a linear relationship, so the answer is b for q6

the ball doesn't keep travelling with a uniform acceleration though, it has no thrust anymore, it will start decelerating at a constant speed, thus its velocity will be a curve

 

[grimreaper]

Yes I agree with L45er simply because both induction motors and electromagnetic braking involve movement, but theres no movement in an induction cook top just eddy currents forming to make heat

 

[grimreaper]

the ball doesn't keep travelling with a uniform acceleration though, it has no thrust anymore, it will start decelerating at a constant speed, thus its velocity will be a curve

yes thats what i thought to - but if you think about it if that were right even D wouldnt be correct - it'd have to be a curve that starts going down the page and heads left instead of the other way around

 

[SuperDuperMicky]

so is the answer to 6 b c or d

Okay, now let's just picture for a moment that the train thingo is travelling at relativistic speeds... ahhahaha i hate relativity

 

[sub]

the ball doesn't keep travelling with a uniform acceleration though, it has no thrust anymore, it will start decelerating at a constant speed, thus its velocity will be a curve

i dont think ur right, gordo. at the point of release, the ball has a certain speed - the same as the train at that point. when released, the ball maintains that speed cos there is no acceleration in the x-axis, thus the train will accelerate away. if u draw verticals from the centre of each time frame ball, then u see that there is a greater distance between each time section, indicating that the train IS accelerating away, which is what is occurring...obviously, this is ignoring air resistance...

 

[sub]

yes thats what i thought to - but if you think about it if that were right even D wouldnt be correct - it'd have to be a curve that starts going down the page and heads left instead of the other way around

d does go down the page and to the left?

 

[gordo]

i put b anyway cause i thought it was right for reasons everyone is saying
but i am reconsidering after thinking that the fram of referrence is accelearting away, hence the horizontal velocity relative to the cart will be accelerating not equally spaced

 

[sub]

but B isnt equally spaced! but the curve thing u sed earlier is...i dont think i understand what ur trying to say gordo...y do u think its d now?

 

[smallcattle]

i put c for q6

 

[sub]

y? to small cattle...

 

[Cactus]

can somebody explain why can't q 11 can't be d?

Electromagnetic braking and induction motors work under the principles of Lenz's Law, where as induction cooking does not.

 

[smallcattle]

y? to small cattle...

cuz i was dumb!! didnt even read the question carefully

if it was observed from a outsider view it should be c, but since the question asked for observer from the frame of reference of the vehicle.. damn it

 

[shazzam]

right...well, i take back my previous comment.

also, for q6, i put b...but apparently u can argue a, cos u get constant acceleration if a= 0 aswell right? so wouldn't that work too?

I sincerely hope the BOS will accept 2 answers again as a consequence of question wording.

 

[superbird]

i reckon q6 is A. basically i thought of galileo's experiment of the crows nest and came to that conclusion. and yeh constant acceleration could also mean a=0

 

[grimreaper]

d does go down the page and to the left?

what i meant is itd have to turn towards the left instead of turning down if you get my meaning

 

[Muzzy]

Here are the actual answers as given by my tutor.........argue if u may but these are all correct:

1. b
2.A
3. D
4. B
5. A
6. C
7. A
8. C
9. A
10. a
11. D
12.B
13 a
14. b
15. b