Physics: Post your doubts here!

[Omar99]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s11_qp_11.pdf
this one please in question no. 13, 18, 19 and 27

 

[syed1995]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w12_qp_11.pdf
question 36 ... syed1995 h4rriet . Thanks in advance guys!

Increasing the variable resistor's resistance will make more PD fall on the variable resistor and less resistance on the fixed resistor! so Voltmeter reading will decrease..

But The ammeter reading will stay unchanged.. since the voltage in parallel circuits is same.. so according to the formula V=IR .. if R remains same I will remain same too.

so Answer should be C.

 

[asangietalks]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w11_qp_12.pdf
no 31 can someone explain why the answer is A?

 

[abruzzi]

Someone please please help me understand the following questions:
http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w05_qp_1.pdf
Qn no. 28, 33, 34
syed1995

 

[Tkp]

hey help me in oct nov 09-28,21,13,12

 

[syed1995]

Someone please please help me understand the following questions:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w05_qp_1.pdf
Qn no. 28, 33, 34
syed1995

x=lambda*D/a
(Lambda/2*D)/2a
x=1/4*Lambda*D/a
so answer should be.. 0.75. A

33

Two Equations

1) R = pL/A
2) Strain = F/A

If strain increases area decreases... according to 2.

Then according to 1 .. If A decreases R increases. So answer is D.

34 ..

draw a line from origin to each of the points... whichever has the lease gradient will give you the answer.. since gradient of the graph is I/V .. and resistance is V/I.. so we need the least gradient. as resistance is 1/gradient so Answer is C

 

[syed1995]

hey help me in oct nov 09-28,21,13,12

Which Variant?

 

[Tkp]

Which Variant?

11

 

[abruzzi]

x=lambda*D/a
(Lambda/2*D)/2a
x=1/4*Lambda*D/a
so answer should be.. 0.75. A

33

Two Equations

1) R = pL/A
2) Strain = F/A

If strain increases area decreases... according to 2.

Then according to 1 .. If A decreases R increases. So answer is D.

34 ..

draw a line from origin to each of the points... whichever has the lease gradient will give you the answer.. since gradient of the graph is I/V .. and resistance is V/I.. so we need the least gradient. as resistance is 1/gradient so Answer is C

Thanks a lot brother
For no. 33, isnt it strain = extension/original length?

 

[syed1995]

Thanks a lot brother
For no. 33, isnt it strain = extension/original length?

Ah my bad.. you'd use

E=Stress/Strain
Strain*E=F/A
If strain increases then Area decreases.

 

[syed1995]

hey help me in oct nov 09-28,21,13,12

12B

R1=R2 is obvious since the force downwards will be same..

So force is R1=2*T1Cos(Theta) and R2=2*T2Cos(Theta) .. as R1=R2 .. As Theta is greater in 1 more force will be required. so T1>T2.

13 No Clue.

21 it's kinda logical.. If you draw a straight line from origin to P.. you will see that the strain energy coming as 0.10 J.. and will also see that there is some area above the line you drew as well.. so there will be more a little more energy than 0.1... so answer is C.

28 No Clue.

 

[tysler]

A particle of mass 2m and velocity v strikes a wall.
The particle rebounds along the same path after colliding with the wall. The collision is inelastic.
What is a possible change in the momentum of the ball during the collision?
A mv B 2mv C 3mv D 4mv

answer is C.. plz someone explain

The collision is inelastic so the speed of the ball after rebounding will be less than v but greater than 0. the answer cant be A or B because the change has to be greater than 2mv since it changes direction. d also cant be because it would make the collision elastic thus c as rebound speed is 0.5v which is in possible range

 

[haha101]

this one too?

B as one block is already in place n we have to stack thre more

 

[h4rriet]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w12_qp_11.pdf
question 36 ... syed1995 h4rriet . Thanks in advance guys!

The reading on the voltmeter decreases because more voltage goes to the variable resistor. The reading on the ammeter isn't changed because the resistance of the resistor it is connected in series with is the same.

 

[h4rriet]

Ty, I still don't understand 14, 19

You have to understand projectile motion to understand 14. The vertical component of the velocity at the highest point during a parabolic trajectory will be 0, and its horizontal component will stay the same throughout.
In 19, all you have to do is put in numbers into the formulas I've given you. You're given the pressure, which is F/A. They want you to find the density. Density=m/v. To get m, you'll need to divide F/g (g is a constant). To get V, you'll need to multiply A with the height, which is given in the question.

 

[h4rriet]

ahmed abdulla I is proportional to (A^2)(f^2). For wave Q, the frequency is halved, so the intensity is divided by four. Then its amplitude is doubled, so the intensity is quadrupled. 4 and 4 cancel out.

 

[Sohail A. Razzak]

...Can anybody help..?

 

[abruzzi]

Ah my bad.. you'd use

E=Stress/Strain
Strain*E=F/A
If strain increases then Area decreases.

Got it.. thanks

 

[zackle09]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w10_qp_12.pdf

can someone please do these questions 12 and 21
for 11..i dont understand why its 2sina shouldnt it just be sina?

 

[abrar]

View attachment 28612 ...Can anybody help..?

c 13.1 right? use v^2=u^2+2as, u=0 for the 1kg mass , a=9.81 and s= 0.5m find v.