Qualification > Sciences
Physics Help HERE ONLY !!
MaNa:
--- Quote from: hala999 on May 26, 2009, 01:12:59 pm ---hey guyz !!!
i need help wid nov 08 1st variant q 5 c
(c) Using a 40 W heater, 16.3 g of ice is melted in 2.0 minutes. The heater is then switched
off. In a further 2.0 minutes, 2.1 g of ice is melted.
Calculate the value of the specific latent heat of fusion of ice from these results.
--- End quote ---
mass -16.3-2.1=14.2
latens heat of fusion= energy
therefore 40*120=4800J
ther fore latent heat of fusion equals
4800/14.2
338J/g
hopes that explians
Tutu_93:
I have a question in may june 2000 paper 3 10 c
What do the mean when they say that Gama rays interaction with gas molecules is very less ??? ???
annie_angel:
can anyone help wid the time base control ; base emitter collector and how the resistance works?? ??? ???
Shogun:
--- Quote from: Bani on May 26, 2009, 01:07:40 pm ---
--- Quote from: Shogun on May 25, 2009, 04:20:04 pm ---2a) put different value of masses on bothe sides of the pivot but make sure tht after using the formula (fxd) (where f=force and d=distance) the product must be same. (then only they are balanced i.e in equilibrium)
the distance are given for each hole to the pivot. so i recomend to take the first hole(with distance 4cm) and add mass 200g at one side of the pivot. and on the other side, add mass 100g on the second hole (with disatnce 8 cm from teh pivot)
so when using the formula "fxd " u get on one side: 200x4=800N
and
on the other side: 100x8=800N
- see both have the same product so it is now they are balanced(in equilibrium)
ans2b) the disc does not move or rotate as u put the mass so they are balanced so no turning effect which means no moment.
c)use formula "fxd"
200x4=800N
100x8=800N
d)this is the force of pivot which is downwar to get tht simply add the masses u put
100+800=900g
but rmember u can choose any mass at any distance but the product with equation "fxd" must be same
thts all,hope this helped, any confusion or difficulties or help u need, im all here
--- End quote ---
Hey,the formula for calculating the moment is f*d, and when we multiply 200g by 4cm, aren't we multiplying the mass by the distance? Aren't we first suppossed to convert the mass into force by multiplying it with 10 (F=ma)? and the unit for moment is supposed to be Nm, isn't it? Please help. Thanks in advance :)
--- End quote ---
true, sorry. so then we have to multiply them by 10, however we get same product, but u must multiply by 10
cuz mass x10 , but first we must convert the masses to killogram then multiply by 10 to get the force. but then thank u bani for correcting me
Shogun:
--- Quote from: annie_angel on May 26, 2009, 03:41:33 pm ---can anyone help wid the time base control ; base emitter collector and how the resistance works?? ??? ???
--- End quote ---
the time base system works for the x plates on the cathode ray osclliscope(CRO), the thing is tht, dpending on time the voltage goes zero between the plates then after acertan period of time say 0.5 secs the voltage gose up to its original value, how does this help? the x plate is ment to let the beams of electrons move horizonataly (left and right) so it hits the screen (on both the left and right side). so to do this, lets say abeam of elctrones in an CRO is coming and as it passes through the x plates(which is charged with postive and negative charge) the beam of electron (which is negative in charge) deflects towards the postive charge plates.
lets say the positive plate is aranged on the right, so when thier is voltage the beam deflects to the right after CERTAIN SET TIME the voltage goes zero (so no charged plate) and the beam returns to its original path (i.e the left side) then again after a certain set time the voltage goes up and the beam of electrons deflects to the right again.. so this is how the beam moves right and left with the help of x plates whic is TIME BASE system.
base emiter stuff...
the base and emmiter and collector wires are used in a transistor. the for the lamp to work (which is uually placed on the path of colletor emitter path) there must be a current on the base current and there must be a suitable potential difference of 0.6v across the base emitter path.
these conditions are needed for the transistor to work which acts as an automatic switch to switch on the lamp (which is usually placed in the collector -emitter path)
resistance stuff,
they say to the current "get the hell outta here" , u see they act as aopposition to the flow of current in the circuit, it does not let the current to pass through. it blocks the path of the current. with variable resistor u can change the amount of blockage, which means u can allow certain ammount of current to pass and flow through.
any more help or confusion or difficulties,plz do ask me.
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