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Physics: Post your doubts here!

S

Snowysangel

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Thought blocker said:
31)
electron would be attracted by the positive charge, so B and D are fundamentally wrong.
now since the electron is moving against the electric field, it will be deflected out of the field by the negative charge.
line of field represents the direction of the field .
so A
35)
answer is A because in tthe question it said there are 2 resistors so as one increases in resistance it requires more voltage so voltage across other one decreases
using formula V/E=R1/R1+R2 to test values you will get something similar to graph A
37)
the contact X would be adjusted around the resistor with 4 kΩ, so the max. n min. limits of p.d. across PQ wud be when its complete resistance is considered and when none is considered. at R = 4kΩ, the resistance across it is 20V
[ 4 /(4+1)] * 25 = 20V
when there is no 4kΩ resistor, p.d. across PQ becomes zero. therefore the answer is B.
Click to expand...
I still don't get 31 and 35...why is the electron deflected out of the field? In 35 why is B wrong...I mean I got those set of values - power decreases initially and then increases according to I2R=P
 
Hadi Murtaza

Hadi Murtaza

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Hadi Murtaza

Hadi Murtaza

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_Ahmad said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s11_qp_13.pdf

Q35,39
Click to expand...
Q.39
Al (27)(13) + α(4)(2) -------> P(30)(15) + _____

The sum of atomic masses of left side is 31, while dat of right side is 30, so either a proton or neutron is missing
THe sum of atomic numbers of left side is 15, n dat of right side is same. Atomic number is the number of protons, n becuz these r both same on either side of da equation, da by product can only b a neutron.
full equation:
Al (27)(13) + α(4)(2) -------> P(30)(15) + N(1)(0)

hence Answer: D
 
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sagar65265

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RoyalPurple said:
papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Physics%20(9702)/9702_s10_qp_11.pdf

quest.16 ans is D ...:confused:
Click to expand...

The Efficiency = (Useful Output energy)/(Total Input Energy).

Let's look at the changes in energy in the process.
Since the kinetic energy of the car doesn't change and remains at v, there is no change in the kinetic energy of the car.
Since friction does not do any work (we can assume this, and even otherwise it is not useful output so it doesn't count) there is no energy lost to internal energy.
However, potential energy does change - the car moves up a height of mgs * sin(α) (Since ΔP.E. = mgΔh, and sin(α) = Δh/s, Δh = s * sin(α) and ΔP.E. = mgs * sin(α)).

Therefore, the useful energy output = mgs * sin(α)

The work we put into the system is the only input to the system; no other influence is exerted by us, so the only input to the system is the work done by our force = F.
This work = F.s = Fs.

So, (Useful Output Energy)/(Total Input Energy) = mgs * sin(α)/Fs = mgsin(α)/F = D.

Hope this helped!
Good Luck for all your exams!
 
RoyalPurple

RoyalPurple

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sagar65265 said:
The Efficiency = (Useful Output energy)/(Total Input Energy).

Let's look at the changes in energy in the process.
Since the kinetic energy of the car doesn't change and remains at v, there is no change in the kinetic energy of the car.
Since friction does not do any work (we can assume this, and even otherwise it is not useful output so it doesn't count) there is no energy lost to internal energy.
However, potential energy does change - the car moves up a height of mgs * sin(α) (Since ΔP.E. = mgΔh, and sin(α) = Δh/s, Δh = s * sin(α) and ΔP.E. = mgs * sin(α)).

Therefore, the useful energy output = mgs * sin(α)

The work we put into the system is the only input to the system; no other influence is exerted by us, so the only input to the system is the work done by our force = F.
This work = F.s = Fs.

So, (Useful Output Energy)/(Total Input Energy) = mgs * sin(α)/Fs = mgsin(α)/F = D.

Hope this helped!
Good Luck for all your exams!
Click to expand...

thank you so much :) i got it :)
all the best to you too :)
 
A

_Ahmad

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DeViL gURl B) said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w11_qp_11.pdf

Guys please question 5 COMPLETE EXPLANATion !!!
Thank u :)
Click to expand...

for finding the largest effect we have to find the percentage uncertainty in each of the variables.

percentage uncertainty in F =(0.01/19.62)*100 =0.05097%

percentage uncertainty in l = (0.002/2.043)*100 =0.0979%

percentage uncertainty in d = 2(0.02/0.54)*100 = 7.41%

percentage uncertainty in x =(0.2/5.2)*100 =3.85%

"d" has the largest effect on the uncertainty in the value of the calculated
Young modulus because it has the highest percentage uncertainty

therefore answer in B
 
Thought blocker

Thought blocker

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_Ahmad said:
for finding the largest effect we have to find the percentage uncertainty in each of the variables.

percentage uncertainty in F =(0.01/19.62)*100 =0.05097%

percentage uncertainty in l = (0.002/2.043)*100 =0.0979%

percentage uncertainty in d = 2(0.02/0.54)*100 = 7.41%

percentage uncertainty in x =(0.2/5.2)*100 =3.85%

"d" has the largest effect on the uncertainty in the value of the calculated
Young modulus because it has the highest percentage uncertainty

therefore answer in B
Click to expand...
Was just this only a concept ._. behind this scary quest :eek: ?
 
Thought blocker

Thought blocker

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_Ahmad said:
for finding the largest effect we have to find the percentage uncertainty in each of the variables.

percentage uncertainty in F =(0.01/19.62)*100 =0.05097%

percentage uncertainty in l = (0.002/2.043)*100 =0.0979%

percentage uncertainty in d = 2(0.02/0.54)*100 = 7.41%

percentage uncertainty in x =(0.2/5.2)*100 =3.85%

"d" has the largest effect on the uncertainty in the value of the calculated
Young modulus because it has the highest percentage uncertainty

therefore answer in B
Click to expand...
What is the use of formula ._. ?
 
O

omeraz

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Can someone please help me with this one from May 2013 Paper 11:
18 A wind turbine has blades that sweep an area of 2000m2
. It converts the power available in the
wind to electrical power with an efficiency of 50%.
What is the electrical power generated if the wind speed is 10ms–1? (The density of air is
1.3kgm–3.)
A 130kW B 650kW C 1300kW D 2600kW
 
Thought blocker

Thought blocker

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_Ahmad said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_11.pdf

Q9,13,29 can anyone please explain.
Click to expand...
9)
answer is B because the ball is falling down with constant acceleration so graph will be an reversed parabola
13)
In order to solve this question, you must imagine three person trying to push an object in any directions. And the minimum resultant force will be when the object is remain at stationary. So at stationary or equilibrium, the resultant force applied by the 3 person will be zero and you can apply the same logic here. 3 forces applied to the object can have a minimum resultant force of 0N.
29)
electron will always move in direction parallel to the direction of the beam. electron repel electron so it would move in opposite direction
 
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