Biology; Chemistry; Physics: Post your doubts here!

[TheStallion-Reborn]

can anyone please xplain the opening and closing of valves during heart beats?

 

[Mustafa Malik]

Q30_i dun know maself i guess its A maybe, wts the crct ans?

its C

 

[Snowysangel]

Food travels from mouth-> Esophagus->stomach->deudenom->ileum->colon->rectum . But at every stage..food is broken down in carbohydrate,fattyacid and Aminoacid

Nooo.... Plasma is only a medium to travel in blood. but in the guts..U have tubes structure that transport.

So the bolus travels without a medium to carry it? Ok got it

 

[Snowysangel]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_s12_qp_11.pdf
Can any one explain Q33?

It's A cause the seed without the testa receives sufficient water while the water in the other two test tubes might have been hindered by the presence of testas in the dish

 

[sourov97]

thanks
but when we look at an object which is not on Camera for example a table why doesn't our eyes behave like a camera and invert it?
sorry if this question is bothering but i never knew it as i am so Dumb

the camera consists of more than one lens...so they adjust the image, maybe,...and i was wrong with what i said...try searching the google if u want clear answers..cause i have no biology and didnt learn the specifications in the eyes.

 

[usama321]

there is an inverted image on our retina..........this is re inverted and corrected by our brain, and our brain sees everything as it is, not everything inverted (not a bio student)

 

[kiara15]

Haha no wonder.

I'm kinda busy right now but I'll try to answer it when I can.
You'd want to post future A Level related questions here: https://www.xtremepapers.com/community/threads/physics-post-your-doubts-here.9860/page-265

already did

 

[ZaqZainab]

the camera consists of more than one lens...so they adjust the image, maybe,...and i was wrong with what i said...try searching the google if u want clear answers..cause i have no biology and didnt learn the specifications in the eyes.

I got it A camera is any sort of light tight chamber (the word camera means "chamber" in Latin) with a pinhole or convex lens in one side. The lens is what "forms" the image on the opposite side of the camera. Your eyes are cameras! They are light-tight chambers with convex lenses which form continuous images on the retinas (light sensitive surfaces) at the backs of your eyeballs. Because of the way light passes through a pinhole or lens, the image is projected to the back of any camera upside down. This is just as true in your eye as it is in your camera! But, you protest, I don't see upside down! No, you don't, because your brain "flips" the image right side up as it comes from your optic nerve. Your digital camera does the same thing electronically before it delivers the image to your viewscreen.
And yeah thanks for your time

 

[sourov97]

I got it A camera is any sort of light tight chamber (the word camera means "chamber" in Latin) with a pinhole or convex lens in one side. The lens is what "forms" the image on the opposite side of the camera. Your eyes are cameras! They are light-tight chambers with convex lenses which form continuous images on the retinas (light sensitive surfaces) at the backs of your eyeballs. Because of the way light passes through a pinhole or lens, the image is projected to the back of any camera upside down. This is just as true in your eye as it is in your camera! But, you protest, I don't see upside down! No, you don't, because your brain "flips" the image right side up as it comes from your optic nerve. Your digital camera does the same thing electronically before it delivers the image to your viewscreen.
And yeah thanks for your time

i should be the one thanking u for such explanation....i merely knew the properties of image formed by the camera lens which is the same for eyes as well...only what we need for o levels..thanks again.

 

[Zoya Shahab]

 

[ZaqZainab]

How do you know the answer for this questions?

 

[usama321]

How do you know the answer for this questions?View attachment 28144

since they are not using the word "specific" which relates to mass, i think the answer would be A, as its temperature rise is the lowest

 

[sourov97]

How do you know the answer for this questions?View attachment 28144

heat capacity is the amount of heat that an object can take before rising its temperature by 1 C....an object with higher heat capacity will need more heat to rise its temperature. since the heat provided is same, the obj with the lowest temperature rise has the highest heat capacity.

 

[Shadman Azad]

heat capacity is the amount of heat that an object can take before rising its temperature by 1 C....an object with higher heat capacity will need more heat to rise its temperature. since the heat provided is same, the obj with the lowest temperature rise has the highest heat capacity.

gud explanation.......so the ans is A.

 

[ZaqZainab]

heat capacity is the amount of heat that an object can take before rising its temperature by 1 C....an object with higher heat capacity will need more heat to rise its temperature. since the heat provided is same, the obj with the lowest temperature rise has the highest heat capacity.

does the volume matter?

 

[sourov97]

does the volume matter?

C = Q/change in temperature............. where C = heat capacity and Q = heat absorbed/heat given (J) [as we consider no heat is lost to the surroundings]
so neither the mass nor volume affects heat capacity.....only energy given and temperature change affects C.

but there is another term specific heat capacity(c) : the amount of heat that an 1kg mass object can take before rising its temperature by 1 C ..... or the heat needed to raise the temperature of a 1 kg mass of an object by 1 C or 1 K......and it is found using the equation
Q = m*c*change in temperature.........or c = Q / (m * change in themerature)
where Q = heat absorbed/heat given......m = mass (kg) and c = specific heat capacity of that object
here, as mass affects c, the volume will also affect c [ as m proportional to V]

 

[shahzadi afia]

C = Q/change in temperature............. where C = heat capacity and Q = heat absorbed/heat given (J) [as we consider no heat is lost to the surroundings]
so neither the mass nor volume affects heat capacity.....only energy given and temperature change affects C.

but there is another term specific heat capacity(c) : the amount of heat that an 1kg mass objectcan take before rising its temperature by 1 C ..... or the heat needed to raise the temperature of a 1 kg mass of an object by 1 C or 1 K......and it is found using the equation
Q = m*c*change in temperature.........or c = Q / (m * change in themerature)
where Q = heat absorbed/heat given......m = mass (kg) and c = specific heat capacity of that object
here, as mass affects c, the volume will also affect c [ as m proportional to V]

all these days i have been thinking them as same....i had the exams like that...but was lucky that this topic didnt come!
still thanks a lot for explaining wonderfully!

 

[Shujaat Khan]

Describe how you would make an experiment to reflect Ultra Violet Rays

 

[Muaaz Iqbal]

Re: Biology,Chemistry & Physics Help Available Here !

thanks for the positive response ! i appreciate it !

anyways anyone has any questions we will be happy to solve them !

I hve que i want to fill this work sheet bcz i am kind a new in olevels

 

[Zoya Shahab]

I hve que i want to fill this work sheet bcz i am kind a new in olevels

I just gave my grade 9 exams so a starter myself but here are wht i think the ans ll be...plz correct if any are wrong
Question 10
a) i) In order to regulate heat
ii) to get accurate temp.via the thermometer
b)water must be changed to a liquid with higher boiling point and range of thermomete should be increased
c)solids have accurate b.p if b.p is below or above from the standard b.p it means that the solids is impure

Question 9
a) descending chromatography, solvent travel in direction of gravity
b) to avoid solvent from hetting dissolved in the liquid
c) to saturate the tank
d) to ensure that solvent has been fully separated. it wud need a longer paper as solvent will travel faster

Question 8
a) i) B ii) A iii) D iv) C
b) i)Ink interferes in the experiment since it is soluble
ii)Ensure maximum chromatography
iii) If they are big they will smudge