Qualification > Sciences
A-Level Physics Paper 1 doubts (MCQ)
krtcobain82:
Guys I need explanations for the following questions.
1) may/june 07 Paper 1
http://www.xtremepapers.me/CIE/index.php?dir=International%20A%20And%20AS%20Level/9702%20-%20Physics/&file=9702_s07_qp_1.pdf
Question no 37 and 40.
2) may/june 09 Paper 1
http://www.xtremepapers.me/CIE/index.php?dir=International%20A%20And%20AS%20Level/9702%20-%20Physics/&file=9702_s09_qp_1.pdf
Question no 5, 7 .
Ghost Of Highbury:
--- Quote from: krtcobain82 on June 02, 2011, 06:15:31 pm ---Guys I need explanations for the following questions.
1) may/june 07 Paper 1
http://www.xtremepapers.me/CIE/index.php?dir=International%20A%20And%20AS%20Level/9702%20-%20Physics/&file=9702_s07_qp_1.pdf
Question no 37 and 40.
2) may/june 09 Paper 1
http://www.xtremepapers.me/CIE/index.php?dir=International%20A%20And%20AS%20Level/9702%20-%20Physics/&file=9702_s09_qp_1.pdf
Question no 5, 7 .
--- End quote ---
Q37) This is a tricky one. Electrical resistance of P - R - pl/A
Let's assume the cross-sectional area of the resistor P is A
Thus, R = px/A
Resistance of Q
Now, the resistance is the combined resistance of all the wires
Say for instance, the resistance one of those wires is px/a (a < A, p, because they're of the same material)
So as the wires are in parallel, the combined resistance => 1/r = 1/r1 + 1/r2 + 1/r3 + ...
= a/px + a/px + a/px + ....
1/r = na/px
r = px/na
Now, As the volumes of the materials used is the same for both resistors, and their length is the same, the cross-sectional area of resistor P
should be the sum of all the cross-sectional areas of the wires in resistor Q
Meaning, na = A
thus r = px/A = Resistance of resistor P
Answer : C
40) The final velocity depends on the acceleration. The one with the least acceleration has the lowest final velocity (v^2 = 2as)
Acceleration, a = F/m
F= EQ
E is constant because V and d are constant.
a = QE/m
E is constant, thus, a is lowest, when the Q/m of the particle is the lowest. That is with C, Li, 3/7
Answer : C
--
5) Best to use elimination in these type of sums. The final displacement can't be zero, thus, you are left with C or D
It can't be C because it doesn't show "constant terminal velocity"
Answer : D
7) Well, to be honest, i thought the answer was C. Well, i'm not sure of A, but that's the answer. The second law deals with force being
the rate of change of velocity times mass, and the first law is about inertia (unless acted upon external force one).
ashwinkandel:
For no. 7 I think its like this. According to first law, the body remains in its state or uniform motion or rest until acted by an external force. If we take this mathematically then F=ma. In absence of external force the equation becomes 0=ma>> or a=0. a=0 tells us that either the body is moving in constant speed or is not moving at all.
Ghost Of Highbury:
--- Quote from: ashwinkandel on June 04, 2011, 03:24:42 am ---For no. 7 I think its like this. According to first law, the body remains in its state or uniform motion or rest until acted by an external force. If we take this mathematically then F=ma. In absence of external force the equation becomes 0=ma>> or a=0. a=0 tells us that either the body is moving in constant speed or is not moving at all.
--- End quote ---
F=ma is the mathematical expression for the second law (Force is the rate of change of momentum). I don't think it's for the first.
ashwinkandel:
Yes, F=ma is the second law. For that question, no. 7, the solution as you said is option A (The first law follows from the second law.) and i tried to show that thing.
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