Physics: Post your doubts here!

[smoothieoeek]

Hai guys,need help here.
My question is if question ask maximum kinetic energy than it is in positin2 ,rite?Thank u.....

Yea it is position 2

 

[periyasamy]

Yea it is position 2

Thank u.

 

[periyasamy]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w09_qp_12.pdf
ok Q11 & 12

I think for question 11,the for both has same reaction force as the weight for the both objets r same.While for the tension thing, I am not sure.Hope someone else here give a hand.
For the second question,some one else explanation ---- first... since applied force is constant, the torque (F*d) will be proportional to d.... torque for 100mm is 3.. so for 150mm , it will be 4.5Nm... so we have to look for the tensions now..torque is the product of force and moment arm.. and the only force present here is the tension in the belt so 3=F*.1 F=30N
for the other wheel, 4.5=F*.15 F=30... so total force is equal to 30N to 30N = 60N...

 

[Jaspreet Dhaliwal]

Hi guys can u please help?

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s12_qp_13.pdf QUESTIONS 10, 28
http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s12_qp_12.pdf QUESTIONS 18,23,24,29
http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w10_qp_12.pdf QUESTIOn 26,33
http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s10_qp_13.pdf QUESTION 18,

Sorry for all questions but im not the smartest at physics ,rregret taking it this year :/ Please help ASAP, it will also be help for you guys too!

 

[periyasamy]

Guys need help here.In this question i get it that the panel 1 and 3 is series together n parallel to 2 ,4.That can be seen by imagining the whole diagram as a circuit.But i dont get it why in option d has a resistor fortm object between points 1 and 3...Thank u.

 

[periyasamy]

Hi guys can u please help?

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_qp_13.pdf QUESTIONS 10, 28
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s12_qp_12.pdf QUESTIONS 18,23,24,29
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w10_qp_12.pdf QUESTIOn 26,33
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_13.pdf QUESTION 18,

Sorry for all questions but im not the smartest at physics ,rregret taking it this year :/ Please help ASAP, it will also be help for you guys too!

For the question 10)---w-t=ma,,,,,,((120-90)9.81)=200a
a=2
v2=u2+2as
substitute in acc value,use the formula,,,,,,u willl get answer.

For question 28----------------------direct one,,,,,,just use the formula n*lamda=dsin theta
maybe u r confused with the angle,must make sure its half of 70 degree n diffraction grating is given.

 

[hina khokhar]

Can anyone post notes on kinematic

 

[iwoeriuyure]

I got a B in AS level physics.with comonpent grades P1-B,P-2 A and a U in Practical.can i still get an Overall A in A level physics?

 

[periyasamy]

Guys for this question .Am i doing the right way?
First do relation that is resistance is inversely proportional to area.Then find area for both using the diameter given .Then relate the resistance with area.Is this rite?

 

[minie23]

http://olevel.sourceforge.net/papers/9702/9702_s13_qp_12.pdf

Kindly help me for question 14, 16, 17 please

 

[periyasamy]

http://olevel.sourceforge.net/papers/9702/9702_s13_qp_12.pdf

Kindly help me for question 14, 16, 17 please

For question 14--------
(0.35*3*9.81)+(0.1*1.4*9.81=(0.15*6*9.81)+ans
ans=2.8Nm

For question 16----is answer b.
if yes then this is the way
80*28/100=112/5
112/5 =potential energy
112/5=mgh
112/5=(o.12)(9.81)h,,,,,,,,,,,,,,,,,only 120 g taken into account as only the arrow has a movement.

For question 17--------mgsinteta*speed=40% of total power mgsinteta=force,,,,,,force*velocity=power
(total m)(9.81)sin30)==40%
100%=ans
Hope it helps.Please tell if the answer u get by this way is differnt from mark scheme...

 

[minie23]

For question 14--------
(0.35*3*9.81)+(0.1*1.4*9.81=(0.15*6*9.81)+ans
ans=2.8Nm

For question 16----is answer b.
if yes then this is the way
80*28/100=112/5
112/5 =potential energy
112/5=mgh
112/5=(o.12)(9.81)h,,,,,,,,,,,,,,,,,only 120 g taken into account as only the arrow has a movement.

For question 17--------mgsinteta*speed=40% of total power mgsinteta=force,,,,,,force*velocity=power
(total m)(9.81)sin30)==40%
100%=ans
Hope it helps.Please tell if the answer u get by this way is differnt from mark scheme...

Thank you loads !

 

[periyasamy]

Hai,guys need help here.Why is this object said to be not in equilibrium?

 

[minie23]

Hai,guys need help here.Why is this object said to be not in equilibrium?

Perhaps the pulling force is much larger than the weight !

 

[mynameisjh]

10 A stationary nucleus has nucleon number A.
The nucleus decays by emitting a proton with speed v to form a new nucleus with speed u. The
new nucleus and the proton move away from one another in opposite directions.
Which equation gives v in terms of A and u?
A v = (A/4 - 1)u
B v = (A – 1)u
C v = Au
D v = (A + 1)u
The answer is B, can anybody please explain this to me ??!!

 

[snowbrood]

10 A stationary nucleus has nucleon number A.
The nucleus decays by emitting a proton with speed v to form a new nucleus with speed u. The
new nucleus and the proton move away from one another in opposite directions.
Which equation gives v in terms of A and u?
A v = (A/4 - 1)u
B v = (A – 1)u
C v = Au
D v = (A + 1)u
The answer is B, can anybody please explain this to me ??!!

i already solved these questions
some important points
the nucleus is initally at rest so its momentum is zero
mass of neutron is equal to proton(
mass of electrons is negligible
lets consider the mass of neutron or proton equal to n
A is neuclon number which is number of protons+neutrons
total number of protons+neutrons times the mass of one of them
total sum of momentum before decaying=after decaying

(nA)*0=n(A-1)u-(n*1)v .

signs change as they are moving in opposite direction
rearraging it gives n(A-1)u=nV
dividing each side with n gives
(A-1)u=V

 

[DumbIdiot]

10 A stationary nucleus has nucleon number A.
The nucleus decays by emitting a proton with speed v to form a new nucleus with speed u. The
new nucleus and the proton move away from one another in opposite directions.
Which equation gives v in terms of A and u?
A v = (A/4 - 1)u
B v = (A – 1)u
C v = Au
D v = (A + 1)u
The answer is B, can anybody please explain this to me ??!!

using POCM( principle.....con momentum)
initial p = final p
initial p of system = 0
final p must also be = o
mass of parent nucleus = Ay( where y is the unified atomic mass constant)
mass of proton = y
mass of daughter nucleus = (A-1)y
o = vy + (A-1)( y )(-u) ( -u cuz u and v are in opposite directions)
rearrange and u`ll end up with v=(A-1)u

u can ignore y as it`ll cancel out eventually

 

[minie23]

mn=(A−1)amump=1amu​

​

pi=pf

0=mnu−mpv

0=((A−1)amu )u−(1 amu) v

(1 amu) v=((A−1)amu)u

v=(A−1)u

 

[Jessie N.]

Help please QAQ

 

[Jessie N.]

Hai,guys need help here.Why is this object said to be not in equilibrium?

The forces don't pass through a same point so not in equilibrium.
Remember that forces passed through a same point are not necessarily equilibrium, but the forces in equilibrium must pass through a same point ^_^