ALL PHYSICS DOUBTS - POST HERE !!

[Syed Kazim]

OK GUYS IMMA SLEEP NOW !!   Its 4 am here !!.. n i need some sleep ..sorry guys if u r questions are pending  

BEST OF LUCK TO ALL !!

Thanks for your help.

[Ivo]

yeah i got that.. how about this one?

The current in a lamp at full brightness is 0.25 A. The flexible cable to the lamp is designed for currents upto 5 A so it can safely carry teh 0.25 taken by the lamp. Which fuse should be inserted in the plug at the other end of the cable?

.. teh answer is 1

Yes, max. required by lamp is 0.25A, so you select fuse which is the next one up.  So 1.5A, is 3A fuse, for example.

[pglasg74]

Excactly, the words in the question say they travel quickly in deeper water, so speed of waves are quicker, wavelength increases, as explained with the formula before.

ooooo riiiiiiiiight tyyyyy so wavelength in shallow is less than wavelength in deep?

[pglasg74]

Thanks for your help.

hey can u explain winter 07 number 21 please?

[Ivo]

ooooo riiiiiiiiight tyyyyy so wavelength in shallow is less than wavelength in deep?

In shallow water, waves travel slowly.  Look at the formula v=f(lambda-wavelength).  So rearange: wavelength=v/f.

So, if v deceases, and frequency is the same, then wavelengh decresases.  Therefore the lines in the diagram get shorter for shallow water.  Opposite for deep water.  Got it?

[pglasg74]

In shallow water, waves travel slowly.  Look at the formula v=f(lambda-wavelength).  So rearange: wavelength=v/f.

So, if v deceases, and frequency is the same, then wavelengh decresases.  Therefore the lines in the diagram get shorter for shallow water.  Opposite for deep water.  Got it?

hey can u explain winter 07 number 21 please?


+ rep 4 u

[Ivo]

hey can u explain winter 07 number 21 please?


+ rep 4 u

Still water surface basically means the middle.  Between the peak and trough.  So B, right?  Think of it this way, the oscillations are perpendicular to wave direction, with maximum reachable amplitude is to the peak and through, and so the middle is the average between the two.

[pglasg74]

Still water surface basically means the middle.  Between the peak and trough.  So B, right?  Think of it this way, the oscillations are perpendicular to wave direction, with maximum reachable amplitude is to the peak and through, and so the middle is the average between the two.

right, so smart lol , thanks 2 last questions please

39, winter 07... the answer's B, but didnt we always talk about decreasing resistance by increasing are (using thicker cables :S) why are we suddenly changing the concept now?

and also, for a fuse.. we always choose the rate next from the device? like if the hairdryer is 1.25 A, ill choose 2 not 3.. but if its 2.5 ill choose 3 not 4?

[Ivo]

right, so smart lol , thanks 2 last questions please

39, winter 07... the answer's B, but didnt we always talk about decreasing resistance by increasing are (using thicker cables :S) why are we suddenly changing the concept now?

and also, for a fuse.. we always choose the rate next from the device? like if the hairdryer is 1.25 A, ill choose 2 not 3.. but if its 2.5 ill choose 3 not 4?

LOL, dunno q.39 isn't about it.

For fuses, yes you're correct.  I'm not sure, but I think fuses generally only have ratings of 1A, 3A, 5A, and 15A; but that doesn't matter .  

[jellybeans]

HIIII!!
some explanation neeeeded please thankyouuuu!

[Weaam]

HIIII!!
some explanation neeeeded please thankyouuuu!

I can helpp yoou!
For the first one Q21, the answer is B, its not A cuz the water can never reach that high after it settles, there are too many big spaces between the wave and the next.
Its not C, cuz when the water settles, itll be highher cuz of the peaks of the waves.
For Q36, just imagine a generator in your head, which parts are always brushing against each other? Its defentily not the coil and brushes, or the coil and the magnet, or even the magnet and the slip ring because they dont even touch! it has to be D, slip ring and brushes.

[jellybeans]

I can helpp yoou!
For the first one Q21, the answer is B, its not A cuz the water can never reach that high after it settles, there are too many big spaces between the wave and the next.
Its not C, cuz when the water settles, itll be highher cuz of the peaks of the waves.
For Q36, just imagine a generator in your head, which parts are always brushing against each other? Its defentily not the coil and brushes, or the coil and the magnet, or even the magnet and the slip ring because they dont even touch! it has to be D, slip ring and brushes.

hahaha ohhh thanks! got the 2nd bit. but not the first bit hahahaha... how dyu know that it'll be higher? and... uhm where the peaks wud be?
THANKS agaiiin

[Weaam]

hahaha ohhh thanks! got the 2nd bit. but not the first bit hahahaha... how dyu know that it'll be higher? and... uhm where the peaks wud be?
THANKS agaiiin

umm... ill put it in another way, when there are waves passing, there are higher bits and lower bits, so its not C because when the water settles, the higher bits will settle too, so making the water level rise a little, get it now?
Ur welcooome! 

[holtadit]

hahaha ohhh thanks! got the 2nd bit. but not the first bit hahahaha... how dyu know that it'll be higher? and... uhm where the peaks wud be?
THANKS agaiiin

This is an application of the amplitude of a transverse wave. The amplitude is the max displacement from a mean position.

[Weaam]

Im having trouble understanding Q13 in O/N 07, could you plz explain, i dunt get why the lvl rises but the pressure stays the same