# Physics: Post your doubts here!

#### Sarosh Jameel

PLZ help me to calculate absolute uncertainties for T^2 .. actually i have just started p5 ..

#### hellen

hellen here you go but don't depend on them as they are so much summarised!
Ty soooo much <<<<<3333

Please ! Some one help me solve this (Question 21) I have a test tomorrow

#### a_wiserME!!

Just remember to use P=v^2/R or P=I^2/R when its asks for power dissipated.
also remember that every resistor are the same so they all have the value of 38.4 ohms
Resistor in Series are added while Resistor in parallel are inversed than added.
and also know that current prefers the least resistive path... such in case of ( Closed Closed Open).

Now try to solve it by yourself . If you cannot understand than feel free to contact.

yep i kinda got it.. thnx

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#### Tozu Fofo

Can anyone please give me good notes for Kinematics unit?

#### shayista547

Can someone explain this to me please
''For the greatest efficiency the external resistance must be much greater than the internal resistance of the cell. However, for the maximum power to be delivered to the external circuit the internal resistance must be equal to the resistance of the external circuit, although the cell will only be 50% efficient.''
Why should the cell be 50% efficient but not fully efficient please?

#### shayista547

When strain is increased,it implies that length decreases according to strain=extension/length
when length decreases,resistance also decrease according resistance=resistivityXlength/area,right?
Then how come the answer is E?Maybe i can't understand the question itself.Help please!!

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#### Physicist

both at same time. only the vertical motion determines the time of fall. the conditions are the same for both.

#### shayista547

Thanks I totally understand it now

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#### shayista547

Help please! :' I can not understand what happens when cells in a battery are wrongly connected like in the following 2 questions.Thanks in advance guys
Question 1 )
Five cells of emf E are connected in series each having internal resistance r. if due to oversight, one cell is connected wrongly, then the equivalent emf and internal resistance are

[a]3E and 5r 2E and 3r

[c] 4E and 5r [d]5E and 3r

question 2)

#### shayista547

Yea me too i think the answer is A as constant speed implies that acce=0
therefore 0=driving force i.e F _ opposing force i.e f
therefore f=F.

#### Wolfgangs

At which point does the body comes to momentarily rest?

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#### Physicist

At which point does the body comes to momentarily rest?
gradient = speed. so, where the gradient is zero. that's at the peak