Biology; Chemistry; Physics: Post your doubts here!

[CoolBreeze]

What effect does the length of spring and mass of bob have on the period of a pendulum???

 

[CoolBreeze]

Suppose there is a distant celestial source which emits pulses of radiation at regular intervals of exactly 100 seconds apart. How many pulses would have been sent to earth in 24 hours?

I didn't get what the question is asking can anyone explain it and tell the answer!?!?!?!

 

[ritesh isuri]

What effect does the length of spring and mass of bob have on the period of a pendulum???

according to the equation T=2pie*root(L/g), as the length of the pendulum increases the period also increases and if see the equation u would notice that there isn`t any need of the mass of the bob to calculate its period so the mass of the bob does not affect the period of the pendulum

 

[ritesh isuri]

hey! i need an answr to a question! lead's proton number is 82! which means it has a complete valence shell! (first shell with 2 electrons, and then 10 more shells with 8 electrons in each, to make a total of 82) with this electronic electronic configuration, how is lead able to react?

maybe its because all shells after the first one do not hold a maximum of 8 electrons!!! by the way in o level u only need to know the electronic configuration of the first 20 elements! nevetherless if u want to know that of lead its 2,8,18,32,18,4

 

[ritesh isuri]

Suppose there is a distant celestial source which emits pulses of radiation at regular intervals of exactly 100 seconds apart. How many pulses would have been sent to earth in 24 hours?

I didn't get what the question is asking can anyone explain it and tell the answer!?!?!?!

the question means that after every 100 seconds a pulse is sent to the earth. suppose a pulse has just been sent then its only after 100 seconds that another pulse will be sent

 

[CoolBreeze]

the question means that after every 100 seconds a pulse is sent to the earth. suppose a pulse has just been sent then its only after 100 seconds that another pulse will be sent

So what's the ans???

 

[CoolBreeze]

I have marked the ans frm the book but I don't understand how they got it???

 

[CoolBreeze]

i do not want to go and calculate feeling too lazy!! but do u have the answer for it?

No!!!!

 

[CoolBreeze]

Explain!!! And give the ans( I don't have it)

 

[rodenzo10]

I need to understand natural polymers plz

 

[CoolBreeze]

Can anyone see if I m correct???

 

[Suchal Riaz]

hey! i need an answr to a question! lead's proton number is 82! which means it has a complete valence shell! (first shell with 2 electrons, and then 10 more shells with 8 electrons in each, to make a total of 82) with this electronic electronic configuration, how is lead able to react?

Assalamu alaikum. there are only 7 periods in periodic table. so there is no element who has more than 7 shells. this means other shells hold more than eight electrons. And don't get confused by complete shells as many 0(8) group elements react as well at high temperature. The reason for reaction is not just completing shells.
if you just too curious(not in syllabus):
And infact there are no 'shell's and the electrons don't orbit the nucleus. There are certain orbitals in each energy level which we usually refer as shells. electrons continuously disappear and re-materialise in each orbital at different and random location. According to Heisenberg's uncertainity principle the location of each electron in a shell at specific time can never be predicted. electrons, like other fundamental particles, are particles as well as waves(like light) so their properties are very different as we think. These things which we learn are not wrong lack many things cause we cant understand these on this level. due to this weird empty orbital story some elements have dual valency, and sometimes noble gasses react to fill empty orbits in last "shell".

hope i did not confuse you.

 

[Suchal Riaz]

View attachment 19181

Explain!!! And give the ans( I don't have it)

ur answer is corrent. It's B. when the ball comes down the it accelerates, when it is at ground there is no force in it(other than friction) and when it goes up, due to gravity it deaccelerates. graph of b best explains this as there is a on y-axis first it increases, then remain idle and then declines.

 

[Suchal Riaz]

Can anyone see if I m correct???
View attachment 19187

sorry for late reply. here's ur answer:
(a):
as it is going against the gravity it's negative acceleration and mass is 1KG
F=ma
F=(1)(-1.6)
F=-1.6N
(b):
V=u+at
0=u-6.6*5
0=u-33(add 33 to both sides)
33 m/s=u

 

[Suchal Riaz]

View attachment 19171
I have marked the ans frm the book but I don't understand how they got it???

(a)maximum is obviously 6 and it occured at 0.6(by graph)
(b)
(i)For speed/time graph the gradient is acceleration. Thus the point where the curve is most tilted towards up(gradient increases as it is tilted toward up) is Y.
(for a curve, the gradient is found by drawing the tangent and taking it's gradient.)
(ii)it top the tangent will be horizontal line and gradient of that is zero so the acceleration is zero at that point.

tell me if it does not make sense.

 

[Daniyal Tanveer]

What are the main chapters to study for ATP CHEMISTRY OLEVELS

 

[Enferno]

What are the main chapters to study for ATP CHEMISTRY OLEVELS

Salts and Identification of ions, and Titration. Its what i know, there are also others check the syllabus.

 

[scouserlfc]

What are the main chapters to study for ATP CHEMISTRY OLEVELS

Basically u must have good command of all the syllabus and titration,salts,rate of reactions and acid bases are really important to see ! !! ! ! !

 

[sweetiepie]

What are the main chapters to study for ATP CHEMISTRY OLEVELS

ATP Notes
http://www.xtremepapers.com/community/threads/atp-notes.20798/

 

[falcon678]

What are the main chapters to study for ATP CHEMISTRY OLEVELS

include moles 2!