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Physics: Post your doubts here!

Unicorn

Unicorn

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Can someone please explain to me the answer to 19?

work done = p * v

so there is a loss of energy....
 

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waleedsmz

waleedsmz

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lavanyamane said:
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s08_qp_1.pdf
Q. 14, 16, 24 please?
Click to expand...

Q.14:
This question is a tricky one indeed. First of all you need to decide at which point will you take the moment. If you look at the diagram, you'll find that you need to avoid the upper force "F" since you will not know the perpendicular distance from this force at any point on the line except at the lowest point, and at the lowest point's moment will be FH. Moreover, if we take the lowest point and calculate the moment about it, it'd be: FH = WA which is not in the given answers. The only alternative to avoid the upper F is to take the moment about the highest point on the ladder, because the moment of the upper F would be zero, and the equation will have 3 components.

By calculating moments about the highest point on the ladder. F x H + W x a = W x 2a
Thus the answer is A.

Will continue your questions in the following reply.
 
waleedsmz

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lavanyamane said:
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s08_qp_1.pdf
Q. 14, 16, 24 please?
Click to expand...

Q.16:
We know that work is the force multiplied by distance along the direction of the force. The direction of the force is obviously the field lines. So the change in work ( the change in potential energy is FS ). To make it more clear, the diagram below explains that all points on the red line have the same potential energy and all points on the orange line has the same potential energy as well because there is no change in the distance along the direction of the force. This is quiet similar to the Gravitational potential energy. If we consider the blue line to be the earth surface and we put equal masses on the pink horizontal line which has the same vertical height from Earth. This means that all the equal masses have the same potential energy.

4.jpg

Ok to know whether the charge lost or gained potential energy. Think of it as a gravitational force as well... If you move an object away from Earth ( There is an attractive force towards the Earth ) then it gains energy (mgh). The field is from the left to right meaning that it is negative to the right and the charge is positive. Thus think of the right side as the surface of the Earth, the object is becomes nearer to the Earth thus it loses energy.

I know this sounds awfully weird and I can explain more if you didn't understand it but its a little bit complex. I honestly think this question depends on the A2 syllabus more than the AS one.

Q.24:
Young Modulus is a property of the material itself not it's length or cross section. Since the two wires are both made of Steel, then they have the same Young Modulus.
 
lavanyamane

lavanyamane

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waleedsmz said:
Q.16:
We know that work is the force multiplied by distance along the direction of the force. The direction of the force is obviously the field lines. So the change in work ( the change in potential energy is FS ). To make it more clear, the diagram below explains that all points on the red line have the same potential energy and all points on the orange line has the same potential energy as well because there is no change in the distance along the direction of the force. This is quiet similar to the Gravitational potential energy. If we consider the blue line to be the earth surface and we put equal masses on the pink horizontal line which has the same vertical height from Earth. This means that all the equal masses have the same potential energy.

View attachment 12447

Ok to know whether the charge lost or gained potential energy. Think of it as a gravitational force as well... If you move an object away from Earth ( There is an attractive force towards the Earth ) then it gains energy (mgh). The field is from the left to right meaning that it is negative to the right and the charge is positive. Thus think of the right side as the surface of the Earth, the object is becomes nearer to the Earth thus it loses energy.

I know this sounds awfully weird and I can explain more if you didn't understand it but its a little bit complex. I honestly think this question depends on the A2 syllabus more than the AS one.

Q.24:
Young Modulus is a property of the material itself not it's length or cross section. Since the two wires are both made of Steel, then they have the same Young Modulus.
Click to expand...
Ah thank youu! I did understand :)
 
lavanyamane

lavanyamane

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waleedsmz said:
Q.14:
This question is a tricky one indeed. First of all you need to decide at which point will you take the moment. If you look at the diagram, you'll find that you need to avoid the upper force "F" since you will not know the perpendicular distance from this force at any point on the line except at the lowest point, and at the lowest point's moment will be FH. Moreover, if we take the lowest point and calculate the moment about it, it'd be: FH = WA which is not in the given answers. The only alternative to avoid the upper F is to take the moment about the highest point on the ladder, because the moment of the upper F would be zero, and the equation will have 3 components.

By calculating moments about the highest point on the ladder. F x H + W x a = W x 2a
Thus the answer is A.

Will continue your questions in the following reply.
Click to expand...
:/ I still don't get it, but thank you :)
 
aditiashok

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hey i'm writing cie for the 1st time as i wanna apply for my graduation from cambridge university....i wanna study arch!!!!!! so i need to hv a levels in maths phy and history....so plz help me with as level phy paper 1....actually the problem is the paper codes are very confusing to me............plzzzz help me out with this.....:(
 
smzimran

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aditiashok said:
dat is wat i dont undrstant!!!! f**k@##$!!//
what's d difference among all d 3?????????
Click to expand...
There are three papers for phy paper 1
namely
11 , 12 , 13

these are called variants scheduled according to diffrent time zones in diffrent countries...

The syllabus code for physics is 9702

and 9702/11 means first variant paper of physics paper 1

9702/12 means second variant paper of physics paper2 ...... etc

Now, did you get it ?
 
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