Biology; Chemistry; Physics: Post your doubts here!

[Awesome12]

HOW ITS DONE?View attachment 42822

There is a formula

............................... Initial Count Rate
Final count rate= ------------------------
............................................2^n

n is the no. of half lives

Initial count rate is 720, and final is 90

90=720/2^n

n = 3


Another formula

.............................. Time period of decay
no. of half lives= ---------------------------
....................................... Half-Life


3 = Time period/ 2400

=7200

 

[kirann]

There is a formula

............................... Initial Count Rate
Final count rate= ------------------------
............................................2^n

n is the no. of half lives

Initial count rate is 720, and final is 90

90=720/2^n

n = 3


Another formula

.............................. Time period of decay
no. of half lives= ---------------------------
....................................... Half-Life


3 = Time period/ 2400

=7200

WHERE DID 3 COME FROMM??

 

[Awesome12]

WHERE DID 3 COME FROMM??

2^n = 720/90

2^n = 8

Using maths

2^n = 2^3

n = 3

 

[kirann]

2^n = 720/90

2^n = 8

Using maths

2^n = 2^3

n = 3

I WAS ASKING ABOUT THE SECOND FORMULA

 

[Awesome12]

I WAS ASKING ABOUT THE SECOND FORMULA

Alright, alright calm down

See i mentioned that 'n' was the no. of half lives in the first formula. In the second formula, i wrote no. of half lives = n

 

[kirann]

2^n = 720/90

2^n = 8

Using maths

2^n = 2^3

n = 3

OH SORRY I THOUGHT ITS ANOTHER WAY

 

[kirann]

Alright, alright calm down

See i mentioned that 'n' was the no. of half lives in the first formula. In the second formula, i wrote no. of half lives = n

Yar nhi ara tha smjh ab agaya

 

[Mahnoorfatima]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s12_qp_22.pdf
Qs 6, c part ii. Shouldn't it be half the wavelength of one wave whereas ms says something else cause by calculation the distance is 0.5 ie 5?

 

[asadalam]

Guys can you explain the i/v graph of a filament lamp and a thermistor?

 

[asadalam]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s12_qp_22.pdf
Qs 6, c part ii. Shouldn't it be half the wavelength of one wave whereas ms says something else cause by calculation the distance is 0.5 ie 5?

Why would it be half?the speed is 0.05 m/s or 5 cm/s and thats the distance travelled in one second.You should revise the waves chapter to clear your concepts.

 

[Mahnoorfatima]

Why would it be half?the speed is 0.05 m/s or 5 cm/s and thats the distance travelled in one second.You should revise the waves chapter to clear your concepts.

I probably should.

 

[princess Anu]

if a parachutist acceleration was previously 5ms^2 but now its 2ms^2 can we say he is decelerating?

 

[Dream.Eater]

Can someone plz explain these mcqs to me????
Awesome12 Dark Destination funky brat asadalam

 

[Dream.Eater]

if a parachutist acceleration was previously 5ms^2 but now its 2ms^2 can we say he is decelerating?

Yes,since his acceleration has decreased.

 

[peacce]

????

 

[Dream.Eater]

????

Ans is C since angle I is equal to angle r, clearly seen.
In B the values are equal but the 2 sets would have the same value. This can't be unless the two incidentrays were parallel to each other so Ans has to be c

 

[princess Anu]

The current changes its direction in Dc motor while rotating? :S
The function of carbon brushes in DC AC is the same? to reduce friction between the commutators?[/quote]

 

[asadalam]

The current changes its direction in Dc motor while rotating? :S
The function of carbon brushes in DC AC is the same? to reduce friction between the commutators?

[/quote]
In DC there are SPLIT rings that reverse the current every half cycle leading to a continuous rotation
In AC there are SLIP rings that allow the wires to carry the emf to the accumulator(cell/battery) easily and without them being entangled in each other.
And in BOTH i think the purpose of carbon brushes is same.

 

[Dream.Eater]

The current changes its direction in Dc motor while rotating? :S
The function of carbon brushes in DC AC is the same? to reduce friction between the commutators?

[/quote]
Yes, its to prevent the copper commutatorfrom wearing out.

 

[Dream.Eater]

The current changes its direction in Dc motor while rotating? :S
The function of carbon brushes in DC AC is the same? to reduce friction between the commutators?

[/quote]
Yes, its to prevent the copper commutatorfrom wearing out.