Physics: Post your doubts here!

[Kanekii]

Pls help me withthisView attachment 64153

Sum of clockwise moment = Sum of anticlockwise moment
3=F*0.05
F=60N
Torque on P
=60*(0.150)/2
=4.5Nm

 

[hellodjfos;s'ff]

well we had base units question then a momentum question where we were to find theta and i guess kinetic energy and then we had kinematics question..about finding velocity displacement and stuff based on graph given with a diagram of a boy on sledge and there were components of weight...involved.Then for electricity,they asked kirchoffs second law, then there wass a diagram of circuit whicih i guess was something like a potentiometer question because we had to find resistance and current and write down relation between two wires and like how to increase the resisitivity or like ratio between length or smth.Then we had an upthrust,weights question where a cylinder was under water and held by a wire,we had to find its weight i guess and we were given the density and fluid it was in,plus we also had to find tension in the wire that was holding it . for waves it was stationary waves,simple question on finding wavelength(a tube was drawn i guess with )..Last question was simple,it was a a B- decay and a quark composition and they asked if nucleas formed after b- decay would be an isotope of the nucleas atfirst or not...Thats all what i rememeber,so can you predict anything?

The paper will definitely start off with base units/confirmation of units along with scalar/vector identification. We would also have the standard momentum questions too. Then, we would surely have a couple of slope questions and a potentiometer/potential divider question. A resistivity and upthrust question would most likely show up. For waves, we could have questions like there is water in a tube with a loudspeaker at top. The water slowly flows out and loud sounds are heard. They would ask something like this(very likely) and possibly phase difference(didn't show up in p2). For nuclear physics, you can expect the standard questions. You can expect a lot more electricity questions in our paper as there were very few electricity questions in p2(the electricity question in p2 was split between forces and electricity).

 

[hellodjfos;s'ff]

Just the 14th one pls!View attachment 64141

As theta is 90, 2 forces, f1 and f2 must have such a magnitude that they form a resultant of 10N in a right angle triangle(upward=downward forces). So apply pythagoras on each option and see which options get the answer 10N. This will turn out to be C or D, so the correct answer is one of them. Now, in equilibrium the resultant moment must also be zero. So if you assume that the pivot is at the point where the wire splits into two other wires, you can figure out that the load f1 is further away from the pivot while f2 is closer. This tells us that f2 has a greater value than f1 since the clockwise and anticlockwise moment must be equal, and when the distance is greater in the formula moment=F*d, the force would be smaller and vice versa. So since f2 is more than f1, C is the finale answer

 

[hellodjfos;s'ff]

for the feb march paper what is the explanation for question 14 ?

Answered it above

 

[hellodjfos;s'ff]

If anyone's got last minute questions, do send

 

[Tom Sewage]

need help can anyone explain how to solve these questions

 

[A*****]

Is this statement regarding 1% correct?? But the extra 0.1 is 10%, not 1%

This one please hellodjfos;s'ff

 

[A*****]

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need help can anyone explain how to solve these questions

For 23, first calculate the wavelength
The distance from a maximum to a minimum is a quarter of a wavelength so multiply the wavelength by 0.25

 

[hellodjfos;s'ff]

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need help can anyone explain how to solve these questions

23: maximum pressure point is compression while minimum pressure point is rarefaction. The distance between rarefaction and compression is half the wavelength. Using v=flamda, find the wavelength and divide it by 2 to get the distance between rarefaction and compression. Wavelength will turn out to be 0.6m, so the answer is 0.3m(B).
27: you see that there is half a loop and it's a fixed string experiment. So in v=flamda, the lamda will be 0.5 which will make the equation v=0.5flamda. Now, if you want a complete wave, you would need to make the equation v=f(lamda). You can do this by increasing the frequency by 2 so that the 0.5 is cancelled out. Hence 2f is the answer(C).
28: d=1/N ---> d=1/300x1000
dsintheta=nlamda
1/300x1000 *sin90=n(600x10^-9)
n=5
This means that there are 5 orders above the central maxima and 5 below. So including the central maxima there is a total of 11 maxima(5+1+5). So the answer is C.
25: There are two sections to this question. First the train approaches the observer then the train goes away from the observer. They are asking you to find the difference in oib

 

[potatocorn12]

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need help can anyone explain how to solve these questions

25 is dopplers effect,first find out two observable frequencies,one will be when car goes away and one will be when car comes towards the person,then find out the difference between them by substracting and that will be your answer because they asked for change in observable frequencies so you cant minus from 400hz

 

[hellodjfos;s'ff]

For 23, first calculate the wavelength
The distance from a maximum to a minimum is a quarter of a wavelength so multiply the wavelength by 0.25

Be careful, the question says maximum and minimum PRESSURE

 

[Kanekii]

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need help can anyone explain how to solve these questions

 

[A*****]

Be careful, the question says maximum and minimum PRESSURE

Oops sorry I was in a haste

 

[hellodjfos;s'ff]

Is this statement regarding 1% correct?? But the extra 0.1 is 10%, not 1%

The explanation given in the picture is difficult to understand.
What I would do is, I would assume that the graph is a triangle(for approximation). So the area of the triangle ends up being 0.1 J. Now as I have shown in the attached file, there is a small area that is being left out when we assume that the shape is a triangle. This means that the total area under the graph is slightly greater than 0.1J. From the options available, 0.11J seems like the most suitable answer, hence C is correct.

 

[hellodjfos;s'ff]

Is 27 B?

C

 

[A*****]

The answer to this is correct to the smallest division but like in chem won't we take it to the nearest HALF OF THE SMALLEST DIVISION?

 

[A*****]

By ref to this question, plz explain that in the equation P=Fv, which force do we take

 

[hellodjfos;s'ff]

View attachment 64162

By ref to this question, plz explain that in the equation P=Fv, which force do we take

The force in P=Fv is meant to be the resultant force. In this question, there is no mention of other forces so we take the resultant force as 180N.

 

[A*****]

The force in P=Fv is meant to be the resultant force. In this question, there is no mention of other forces so we take the resultant force as 180N.

But we derive this equation from the equation of work right? So shouldn't the force be the one in the direction of work being done??

 

[hellodjfos;s'ff]

But we derive this equation from the equation of work right? So shouldn't the force be the one in the direction of work being done??

That is true, but power is a scalar quantity so the direction of the force or velocity don't matter.