Physics: Post your doubts here!

[Furqan Azam]

for 33 see solution 387 at
http://physics-ref.blogspot.com/2015/02/physics-9702-doubts-help-page-71.html

How do you ask that blogger to solve some questions. I mean where to post the comments?

 

[asadalam]

Can someone explain these to me? Physicist

 

[asadalam]

Many of these have already been solved. Could you search in the specific paper at
http://physics-ref.blogspot.com/2014/05/physics-9702-notes-worked-solutions-for.html

I searched the blog for june 2003 but only two of these i found solved (35 and 10) rest i couldnt find :/ Any help?

 

[Ahmed Aqdam]

Can someone explain these to me? Physicist

View attachment 54164 View attachment 54165 View attachment 54166 View attachment 54167 View attachment 54168

20. Here
5. Here
22. There are three springs with extension x so the total extension due to weight W is 3x. The extension due to 2W will be 6x. When one spring is removed and two are left the extension on both due to 2W will be 3x.

Just a note on 35: This is probably the most repeated question ever. The trick here is to know that the d in the formula E=V/d is the separation of the plates and not the distance from the plates. The separation remains constant and so does the electric field.

 

[69ermalik007]

Plz help..... I cant solve this question

 

[princess Anu]

why is it D? :S :/

 

[princess Anu]

why is P < R ?

 

[princess Anu]

see 325 at
http://physics-ref.blogspot.com/2015/01/physics-9702-doubts-help-page-56.html

how do we know if the sphere is stationary or moving up/ down ? :/ may be its weight is greater than upthrust,who knows? how can we assume it to be moving upwards & conclude that R is greater than P :/

 

[Farhad221]

the answer is A can anyone explain with the calculation

 

[Farhad221]

And this one the answer is D

 

[Ahmed Aqdam]

the answer is A can anyone explain with the calculation

The extension provided by each spring is e.
X: Springs are in parallel so extension will be 1/e+1/e=1/(resultant extension). Hence resultant extension is e/2.
Y: For both the series combinations the extension is 2e. Considering the parallel combinations: 1/2e+1/2e=1/(resultant extension). Hence resultant extension is e.
Z: For parallel springs extension is e/2 and when added to the 3rd spring the total extension is 3e/2.
So order of increasing extension is X-Y-Z.

And this one the answer is D

According to Young Modulus formula: F=EAe/l, force is directly proportional to area and inversely proportional to length.
The tension in P is T.
Tension in Q will be halved due to the double length and will be halved further due to the half cross-sectional area. Hence it will be T/4.
(T)/(T/4) is 4 or 4/1.

 

[Ahmed Aqdam]

Help needed

The weight of one person is 588.6 N so weight of 20 people will be 11772 N.
The force in the direction of motion is 11772*30/60=5886 N.
Multiply this by 0.75 to get the power which is needed to drive the passengers.
Add 2.0 kW as it's the power to drive an empty escalator.

 

[69ermalik007]

Need desperate help.....

 

[69ermalik007]

and in these..........

 

[Mathemagical]

and in these..........
View attachment 54255 View attachment 54255 View attachment 54256

Question 24: Imagine the wave moving from left to right. Point C would be moving upwards with maximum speed because it precedes a crest.

Question 6: Read the question carefully. The question asks for average velocity, not average speed. Since the graph clearly shows motion in the opposite direction, the 2 distances are equal and hence displacement is zero. Therefore, average velocity = Total Displacement/Time = 0.

 

[princess Anu]

why is 2 wrong?

 

[Mathemagical]

why is 2 wrong?

Liquids can flow due to their molecular characteristics. The bonds holding the liquid molecules together are relatively weak and therefore the molecules can move over one another.

 

[princess Anu]

ans is C... y does the ammeter reading remain unchanged??

 

[qwertypoiu]

ans is C... y does the ammeter reading remain unchanged??

The ammeter is reading the current in that line down there flowing through that resistor next to it. The resistor has potential difference V across it equal to that of the emf of the battery since it is a parallel circuit. The resistor also has its own resistance R. Both of these quantities do not change when the variable resistor's resistance increases. Therefore the current remains the same. Had the ammeter been placed in that branch with the variable resistor, the reading would have decreased.

 

[princess Anu]

The ammeter is reading the current in that line down there flowing through that resistor next to it. The resistor has potential difference V across it equal to that of the emf of the battery since it is a parallel circuit. The resistor also has its own resistance R. Both of these quantities do not change when the variable resistor's resistance increases. Therefore the current remains the same. Had the ammeter been placed in that branch with the variable resistor, the reading would have decreased.

But the fact that the overall resistance in the circuit increases, doesn't that change the current in the circuit?