Physics, Chemistry and Biology: Post your doubts here!

[Ahmed Al Hilali]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_s11_qp_32.pdf
last question
half life = 8 h
for completing the curve ,, do I continue dividing the count rate and adding 8 hours to plot a point ?

 

[Louise29]

Good day, I have a question here: to find refractive index, we use sin i/sin r. But there are cases when we have to switch to sin r/sin i. I would like to ask, when do we switch?

 

[sunnykong]

Anyone who could explain Lenz’s law plzzzz

 

[AlphaWolf]

Hello,
I dont understand how you find the speed of this question. 3(B). What do you have to do? Please help.

 

[Omar Shabib]

all physics definitions plz

 

[Lama AN]

A QUESTION IN PAPER 3 PHYSICS
2008 NOVEMBER OCTORBER VARIANT 31 ..
I NEED SOMEONE TO EXPLAIN IT FOR ME .

 

[Rania1]

A QUESTION IN PAPER 3 PHYSICS
2008 NOVEMBER OCTORBER VARIANT 31 ..
I NEED SOMEONE TO EXPLAIN IT FOR ME .

Which

 

[irfan.kheerdali]

notes and questions for chemistry paper 2

 

[Othman]

Bio ; Paper 31
There was a question about crabs that live in deep sea have white outerlayer.
So I said it's mutation that natural selection chose that melanin is not required as there is no sunlight. So the crab becomes white ( Albino ).

 

[Faaiz Haque]

http://papers.xtremepapers.com/CIE/Cambridge%20IGCSE/Physics%20(0625)/0625_w10_qp_33.pdf
Question 1 a) iii
Thanks

 

[maria moreno]

can someone please help me with electrical motors? (physics) I'm so stuck

 

[ZaqZainab]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Physics (0625)/0625_w10_qp_33.pdf
Question 1 a) iii
Thanks

Tricky ain't it?
Now you know the equation Speed=Distance/Time But this is for constant speed :/ but the graph does not have constant speed
Now yo need to know the Distance in the first 3 second because we have to remove this distance from triangle and rectangle
using area under the graph =1/2*8*3 you will get 12 so in the first 3s 12m traveled
What about the other time how much in the other time 100 is the total so 100-12 will give you for the other
which is 88 so now the are under the triangle and rectangle = distance traveled which is 88 Damn Here is an attachment to help i suck at explaining

 

[Faaiz Haque]

Tricky ain't it?
Now you know the equation Speed=Distance/Time But this is for constant speed :/ but the graph does not have constant speed
Now yo need to know the Distance in the first 3 second because we have to remove this distance from triangle and rectangle
using area under the graph =1/2*8*3 you will get 12 so in the first 3s 12m traveled
What about the other time how much in the other time 100 is the total so 100-12 will give you for the other
which is 88 so now the are under the triangle and rectangle = distance traveled which is 88 Damn Here is an attachment to help i suck at explaining

I get how you find the area of the yellow part, but what do you do after that? I don't understand the last part : area of yellow=1/2*(11.2*x)=1.6 80-x = 7.7
What is x? And why are we finding the area of yellow again when we just found it..? I'm confused, please explain if you can, or someone else, thanks .

 

[GorgeousEyes]

Pleaaase anyone could explain to me in convection , Land and sea in night and sunshine thingy ,, I am confused

 

[ZaqZainab]

can someone please help me with electrical motors? (physics) I'm so stuck

Sure
What is an Electrical motor? An electric motor is a device that transfers electrical energy into rotational energy.
How is it Done?Something that spins round has rotational energy.
Rotational energy is a form of kinetic energy.
How do they work? The catapult effect (motor effect) is used to make a simple electric motor spin round. The wire is pushed in the opposite direction if the direction of the current through it is reversed.
Where is the wire from? In a motor, the wire is wound around a central block called an armature.
How does the armature rotate?A spindle(Axis) through the armature allows it to rotate. The current flows in opposite directions on each side of the armature, so one side is pushed while the other is pulled. This makes the armature rotate.
What are split ring commutator?A split - ring commutator (sometimes just called a commutator) is a simple and clever device for reversing the current direction
through an armature every half turn. If it is present the current will flow in one direction(ONE DIRECTION )
What are those made from?The commutator is made from two round pieces of copper, one on each side of the spindle. A piece of carbon (graphite) is lightly pushed against the copper to conduct the electricity to the armature. The carbon brushes are on the sides of the copper when the commutator spins.
How do they work? As the motor rotates, first one piece of copper, then the next connects with the brush every half turn.

​

 

[lord 10]

Bio ; Paper 31
There was a question about crabs that live in deep sea have white outerlayer.
So I said it's mutation that natural selection chose that melanin is not required as there is no sunlight. So the crab becomes white ( Albino ).

I didn't solve the last question and the Second Page ,,,,,,,,,,,,, Am Still have chance to get A*????????

 

[GorgeousEyes]

Pleaaase anyone could explain to me in convection , Land and sea in night and sunshine thingy ,, I am confused

Anyone ??

 

[Othman]

hey when did u took the exam

Today

 

[GorgeousEyes]

Okay , I found his .. During the day, the sun warming the land also warms the air. Since land heats up quicker than water does, the air over land gets warmer than the air over the water. Consiquently, the warmer air, being less dense moves up. To fill its place the cooler air over the water moves in to fill its place creating whats known as a Sea Breeze. Reversly, at night the land cools down faster than the water does, and creates a Land Breeze. .

 

[lord 10]

Idk

from where u r