Physics: Post your doubts here!

[Thought blocker]

he is moving up at rate of 50cm/s means 0.5m/s
his mass is 80KG so his weight is almost 785N
power = work done per second= Force * distance/second = 785*0.5=392=0.39KW

LOL I GOT 392 then I thought I might had made some mistake LOL

 

[Thought blocker]

if he is at constant speed there is no resultant force so all forces cancel out so
air resistance = weight
kv=mg
v=mg/k
kinetic energy = 1/2 mv² = 1/2 m (mg/k)² = 1/2 m³g²/k² = m³g²/2k²

Acha!!

 

[Suchal Riaz]

View attachment 44977 View attachment 44978

m1g is weight at one side. m2g is weight at other side. their difference is balanced by motor.
so the resultant force is m1g - m2g = g(m1-m2)
motor provide the same amount of force to keep the resultant = o
power = Fv = g(m1-m2)*v

 

[Thought blocker]

View attachment 44977 View attachment 44978

Ok..

 

[Asad Moosvi]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w10_qp_12.pdf

Q 27 anyone?

 

[Thought blocker]

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

Q 27 anyone?

Let the distance between the double slit and the screen be 1m initially.
When the distance is increased BY 2m the NEW distance is 3m.
Using the formula:
Wavelength= (fringe seperation x distance between the double slits)/ distance between the screen and the slits.
Wavelenght=600nm=600x10^-9m.
Fringe seperation= 3mm= 3x10^-3m
Distance between screen and slits= 3m (1+2)
Distance between the double slit=?
Put these values in the formula, the final answer is 6x10^-4m =0.6mm
Hence the answer is B.

 

[Princess Raven]

Can someone explain q 17,29,30 of mj 12 v 12
And question 40,20,7,3 of mj 07
PLZZ

 

[Thought blocker]

Can someone explain q 17,29,30 of mj 12 v 12
And question 40,20,7,3 of mj 07
PLZZ

s12_s12
17)
At the bottom height is zero so mgh = zero
now going upwards..
2 block has height = 1 so mg1h
3 block = mg2h
4 block = mg3h
Sum up P.E ans is 6mgh

29)
c = f * λ
We know f = 1 / t
so c = 1 / t * λ
t = λ / c
now it took 3 wavefronts to reach XY to P
so t = 3λ / c

30)
Its a standing wave, so the 33cm is the distance between two nodes. The wavelength thus becomes .66m. F = 330/0.66 = 500. T = 1/500 = 0.002s = 2ms. B is the right answer

s07_1
Suchal Riaz
me gtg

 

[Asad Moosvi]

Let the distance between the double slit and the screen be 1m initially.
When the distance is increased BY 2m the NEW distance is 3m.
Using the formula:
Wavelength= (fringe seperation x distance between the double slits)/ distance between the screen and the slits.
Wavelenght=600nm=600x10^-9m.
Fringe seperation= 3mm= 3x10^-3m
Distance between screen and slits= 3m (1+2)
Distance between the double slit=?
Put these values in the formula, the final answer is 6x10^-4m =0.6mm
Hence the answer is B.

I know that, but why did you assume the initial distance between the double slits and the screen to be 1m? If we assume something else, we'll get a different answer.

 

[MYLORD]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s10_qp_11.pdf q 5,16,20,27,

 

[Suchal Riaz]

Can someone explain q 17,29,30 of mj 12 v 12
And question 40,20,7,3 of mj 07
PLZZ

3:
simple. the speed must have units m/s
in (a) √(gλ)=(m²/s²)^½ = m/s
no need to check rest of them
7:
O level vectors: x=v-u
v-u = at
so x=at

20:
All i can do is visualise which parts are bending in what way. X and Y are being stretched but Z is being pressed/compressed.
X and Y experience tension while Z experiences compression. just visualise.
40:
the particle which completes acceleration with the lowest speed must have had lowest acceleration as the distance is same.
F is not the same. force directly proportional to charge. acceleration = F/m so acceleration will depends on charge and mass. A ∝charge/mass
so find charge to mass ratio. the one with smallest ratio has lowest acceleration therefore lowest speed at the end.
(a)1/1=1
(b)2/4=0.5
(c)3/7=0.428...
(d)4/9=0.44...
smallest is (c)

 

[Suchal Riaz]

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

Q 27 anyone?

x=dλ/a

in case 1,
1E-3=d600E-9 / a
so d=1667a
in case 2:
3E-3=(d+2)*600E-9 / a
a=(d+2)*600E-9 / 3E-3
a= (1667a + 2)2E-4
a-0.333a=4E-4
a=4E-4 / 0.667
=6E-4m=0.6mm
this was the only way it came in my mind. maybe ZaqZainab or someone else can tell a shorter way. if no shortway comes into your mind atleast do complete it through complete procedure.

 

[Asad Moosvi]

x=dλ/a

in case 1,
1E-3=d600E-9 / a
so d=1667a
in case 2:
3E-3=(d+2)*600E-9 / a
a=(d+2)*600E-9 / 3E-3
a= (1667a + 2)2E-4
a-0.333a=4E-4
a=4E-4 / 0.667
=6E-4m=0.6mm
this was the only way it came in my mind. maybe ZaqZainab or someone else can tell a shorter way. if no shortway comes into your mind atleast do complete it through complete procedure.

I solved it the same way now, but this takes too long

 

[..sacrifice4Revenge..]

x=dλ/a

in case 1,
1E-3=d600E-9 / a
so d=1667a
in case 2:
3E-3=(d+2)*600E-9 / a
a=(d+2)*600E-9 / 3E-3
a= (1667a + 2)2E-4
a-0.333a=4E-4
a=4E-4 / 0.667
=6E-4m=0.6mm
this was the only way it came in my mind. maybe ZaqZainab or someone else can tell a shorter way. if no shortway comes into your mind atleast do complete it through complete procedure.

E denotes?
i dnt get this :/

 

[Kamihus]

E denotes?
i dnt get this :/

2E-4 is 2*10-4

 

[selena]

if he is at constant speed there is no resultant force so all forces cancel out so
air resistance = weight
kv=mg
v=mg/k
kinetic energy = 1/2 mv² = 1/2 m (mg/k)² = 1/2 m³g²/k² = m³g²/2k²

Thankyou so much

 

[sweetym]

http://papers.xtremepapers.com/CIE/...Level/Physics (9702)/9702_w09_qp_12.pdfnumber 6,8,11,21,25,34

 

[Kamihus]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w09_qp_12.pdfnumber 6,8,11,21,25,34

6: Area under graph in last 2 seconds=Area of trapezium
0.5(6+12)*2=18m

8: Elastic collision so they will move in opposite directions. Only A and B but in B momentum is not conserved. Thought blocker can explain you this one better.

21: Convert diameter to radius then pi*r^2 to get area. force/area to get stress and stress/young modulus to get strain. Multiply by 100 to get the percentage.

25: 7 maxima are on one side, 7 are on the other and 1 is the zero order maxima so total 15.

34: pd across R1 is ratio of R1 and total resistance. Ratio is same as ratio pd divided by total pd or emf.

 

[Kamihus]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w11_qp_11.pdf
Q32 How is torque anti-clockwise?
http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w12_qp_11.pdf
Q14 Ans is A.

 

[sweetym]

6: Area under graph in last 2 seconds=Area of trapezium
0.5(6+12)*2=18m

8: Elastic collision so they will move in opposite directions. Only A and B but in B momentum is not conserved. Thought blocker can explain you this one better.

21: Convert diameter to radius then pi*r^2 to get area. force/area to get stress and stress/young modulus to get strain. Multiply by 100 to get the percentage.

25: 7 maxima are on one side, 7 are on the other and 1 is the zero order maxima so total 15.

34: pd across R1 is ratio of R1 and total resistance. Ratio is same as ratio pd divided by total pd or emf.

6: Area under graph in last 2 seconds=Area of trapezium
0.5(6+12)*2=18m

8: Elastic collision so they will move in opposite directions. Only A and B but in B momentum is not conserved. Thought blocker can explain you this one better.

21: Convert diameter to radius then pi*r^2 to get area. force/area to get stress and stress/young modulus to get strain. Multiply by 100 to get the percentage.

25: 7 maxima are on one side, 7 are on the other and 1 is the zero order maxima so total 15.

34: pd across R1 is ratio of R1 and total resistance. Ratio is same as ratio pd divided by total pd or emf.

6: Area under graph in last 2 seconds=Area of trapezium
0.5(6+12)*2=18m

8: Elastic collision so they will move in opposite directions. Only A and B but in B momentum is not conserved. Thought blocker can explain you this one better.

21: Convert diameter to radius then pi*r^2 to get area. force/area to get stress and stress/young modulus to get strain. Multiply by 100 to get the percentage.

25: 7 maxima are on one side, 7 are on the other and 1 is the zero order maxima so total 15.

34: pd across R1 is ratio of R1 and total resistance. Ratio is same as ratio pd divided by total pd or emf.

I also Have doubt in this question 11,12,13.. Sorry..but Thank you fr ur help..