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Physics paper 1 doubt

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Got Tech? GO TECH:

--- Quote from: Ari Ben Canaan on May 25, 2010, 12:37:15 pm ---It would be D.

The dam wall needs to be thicker at the bottom. WHY U ask ?

Because pressure INCREASES with depth thus the pressure UNDERWATER is larger than at the surface.

So thicker wall at the bottom to resist the pressure.

GOT IT ?   ;)

--- End quote ---

Ahh, I see, Thanks a lot!!!
+1 for the quick answer :D

holtadit:
No problem ;)

Weaam:
Ive a question, its question37 and 19 in oct/nov 08, and i cant understand them.
Could anyone help me? :-\

dsiddiqi11:

--- Quote from: weaam on May 25, 2010, 02:45:41 pm ---Ive a question, its question37 and 19 in oct/nov 08, and i cant understand them.
Could anyone help me? :-\

--- End quote ---

 
37.this is a property of a thermistor:AS TEMP ACROSS THERMISTOR INCREASES THE RESISTANCE DECREASES. so in the question, it says, temp across thermistor increases, so resistance decreases, and when resistance decreases, more current can flow towards the lamp (current and resistance are inversely proportional) , and therefore it gets brighter. ANSWER IS C.

19.hot air always rises and cold air moves down, so the gap is down, so from the heater the hot air goes up and cold air goes down.

   GET IT!!!! ;)

Snake:

--- Quote from: weaam on May 25, 2010, 02:45:41 pm ---Ive a question, its question37 and 19 in oct/nov 08, and i cant understand them.
Could anyone help me? :-\

--- End quote ---

Q37=C: This is because the Thermistor gets heated, so Voltage decreases and remember R=V/I, if V decreases then R decreases allowing a stronger current hence brighter lamp!
Q19=B: This is to do with Convection Currents, remember Hot rises, Cold sinks. When the heater heats the hot air rises above the cupboard while the cold air would normally have to go under the cupboard and towards the heater. See the attached picture!

Hope I helped :)

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