Physics: Post your doubts here!

[daredevil]

for the first question there is a uniform decrease in velocity(rate of change of height) because the acceleration is constant,no?

no i don't think so. it's parablic motion. have you done parabolic yet? i don't know maybe i'm wrong but that's what i think is right. maybe someone else canhelp. @A star @syed1995 anyone?

 

[Mubbasher Iqbal]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w11_qp_12.pdf
q16

 

[syed1995]

no i don't think so. it's parablic motion. have you done parabolic yet? i don't know maybe i'm wrong but that's what i think is right. maybe someone else canhelp. @A star @syed1995 anyone?

highlighting me for an AS question.? Good Call!

Well first of all.. there will always be horizontal component of velocity so that's that which will be uniform since Gravitational Acceleration has no effect on it. Now in the vertical component of Velocity Gravitational Acceleration will affect it.. as it goes up the acceleration will be -ve and there will be a decrease in speed and when it goes down acceleration will be positive and there will be an increase in the velocity... it won't be uniform because V^2 = (Vhor^2 + Vver^2) (Simple Pythagoras Theorem).. a square root will never give you a straight line remember that so answer is D.

 

[Snowysangel]

Could sb please tell me why, when generating electrical power, the electrical power output would be less than the power available from a source such as the wind or the sun. How would power be lost

 

[daredevil]

highlighting me for an AS question.? Good Call!

Well first of all.. there will always be horizontal component of velocity so that's that which will be uniform since Gravitational Acceleration has no effect on it. Now in the vertical component of Velocity Gravitational Acceleration will affect it.. as it goes up the acceleration will be -ve and there will be a decrease in speed and when it goes down acceleration will be positive and there will be an increase in the velocity... it won't be uniform because V^2 = (Vhor^2 + Vver^2) (Simple Pythagoras Theorem).. a square root will never give you a straight line remember that so answer is D.

hahha making good calls *like a boss*

@SilverCrest here you go

 

[hamzashariq]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w08_qp_1.pdf
Q.10
the answer is D. but why?? shouldn't it be u1-u2 since they are in opposite direction??

 

[daredevil]

Could sb please tell me why, when generating electrical power, the electrical power output would be less than the power available from a source such as the wind or the sun. How would power be lost

power is wasted in the form of heat energy, sound energy, light energy, etc.
it is sometimes case-by-case basis so do see whether the method or process you are talking about does involve these energy changes or not.

Actually nothing in the practical world is 100% efficient. Some energy is always lost in mostly at least one of the mentioned forms, so when speaking practically power output is always less than power input.

 

[asma tareen]

Can anyone explain kirchoff's laws :/

 

[reachonlyme]

Any doubts in O levels(math,physics and chemistry),u can get help..
Look at the free O levels Statistics class
just follow the link
http://www.wiziq.com/course/40536-free-igcse-math

 

[shazmina]

Can someone help me with Qs no 17 of this paper
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s04_qp_1.pdf
& Qs no 14 of this paper
http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s05_qp_1.pdf
Thanks in Advance

 

[daredevil]

Can someone help me with Qs no 17 of this paper
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s04_qp_1.pdf
& Qs no 14 of this paper
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s05_qp_1.pdf
Thanks in Advance

Q.17
E(x)/E = [(2m*v^2)/2] / [(m(2v)^2)/2)]
= [mv^2]/[2mv^2]
= 1/2

So X has half the kinetic energy of Y.
answer : A

 

[shazmina]

Q.17
E(x)/E = [(2m*v^2)/2] / [(m(2v)^2)/2)]
= [mv^2]/[2mv^2]
= 1/2

So X has half the kinetic energy of Y.
answer : A

Thanks alot sis

 

[daredevil]

Thanks alot sis

no problem

 

[periyasamy]

Hi guys .Anyone can help me with this question.Thank u a lot.

 

[shazmina]

Can someone help me with Qs no 34 of this paper
http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s11_qp_11.pdf
Thanks in advance

 

[Snowysangel]

Hi guys .Anyone can help me with this question.Thank u a lot.

Isn't it mgh= (6x10^24)*(1.3x10^4)*9.81 ?

 

[Kim Shaw]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w08_qp_1.pdf
Q.10
the answer is D. but why?? shouldn't it be u1-u2 since they are in opposite direction??

The collision is perfectly elastic. hence, the relative speed of approach=relative speed of separation.
Imagine 2 bodies of equal masses (B1 and B2) approaching each other...and on collision move away in opposite directions.
if B1 moves 10 steps towards B2, and B2 moves 5 steps towards B1, then they approached by 5+10=15steps
thus rel.speed of approach is u1+u2

similarly, if after collision, B1 moves towards B2 by 1 step, and B2 moves away from B1 by 1000 steps, then both bodies are separated from each other by 1000-1=999 steps.
thus rel.speed of separation is V2-V1
put both together and tada!
u1+u2=v2-v1

 

[Kim Shaw]

Can someone help me with Qs no 34 of this paper
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s11_qp_11.pdf
Thanks in advance

R=(pl)/A
A=L^2
When A is substituted in 1st equation, R=p/l
now V=l^3
l=(l^3)^(1/3)
thus, l=V^(1/3)
replacing this in 2nd equation... R=p/(V^(1/3))
answer C

 

[periyasamy]

Isn't it mgh= (6x10^24)*(1.3x10^4)*9.81 ?

Thanks buddy,but the answer is 4.19*10^7.Your solution gives me answer of 7.6*10^29.

 

[shazmina]

R=(pl)/A
A=L^2
When A is substituted in 1st equation, R=p/l
now V=l^3
l=(l^3)^(1/3)
thus, l=V^(1/3)
replacing this in 2nd equation... R=p/(V^(1/3))
answer C

Thanks you sis