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Physics: Post your doubts here!

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http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s09_qp_4.pdf
help please! 6(b)(i) why does the fact that the force on the magnet is downwards mean that the force on the wire is upwards?
Force on wire is upwards according to newtons third law.
Use Flemings left hand rule. Thumb will point upward, second finger in direction from x to y. So first finger will be from pole p to other pole. Thus pole p is north pole as magnetic field direction is from north to south.
 
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can somone pleassseeee help me in this question??
this paper is summer 2011 paper 52 question 2
the question says that it is suggested that V and R are related by the equation

V = F E /R + E

Where F is the resistance of the fixed resistor in the circuit and E is the e.m.f of the cell
a graph is plotted of V/E on the Y axis against 1/R on the X axis. Express the gradient in terms of F

can someone explain why the gradient answer is F ?
Thanks in advance !!!
 
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Part b says to calculate the new height gained by the ball,its kinetic energy is 90% of what was before
past.JPG
I went through this working and was able to calculate the right answer but the ms says to just take the 90% of the height and not going through the long working,the right answer scores only 1/2 why is that?What concept am i missing?
new.jpg
 
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can somone pleassseeee help me in this question??
this paper is summer 2011 paper 52 question 2
the question says that it is suggested that V and R are related by the equation

V = F E /R + E

Where F is the resistance of the fixed resistor in the circuit and E is the e.m.f of the cell
a graph is plotted of V/E on the Y axis against 1/R on the X axis. Express the gradient in terms of F

can someone explain why the gradient answer is F ?
Thanks in advance !!!
Y = mx + c
Y = V/E
x = 1/R
V/E = m(1/R) + c
m = F(E/E)(1/R)
m = F
 
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Part b says to calculate the new height gained by the ball,its kinetic energy is 90% of what was before
View attachment 59692
I went through this working and was able to calculate the right answer but the ms says to just take the 90% of the height and not going through the long working,the right answer scores only 1/2 why is that?What concept am i missing?
View attachment 59694
Your method is correct, but it can be done in a simpler way. Make use of the concept of conservation of energy. The P.E at the h1 (the initial height from which the ball was dropped), is converted into K.E fully when it hits the plate. That means that

P.E at h1 = K.E

Now after leaving the plate, the K.E (which is 90% of the K.E before hitting Or 90% of P.E at h1) is converted into P.E as it reaches h2. So,

90/100 * P.E at h1 = P.E at h2
90/100 * m g h1 = m g h2
90/100 * h1 = h2
 
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PLEASE tell me how to solve it.
correct answer is C.
 

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PLEASE tell me how to solve it.
correct answer is C.
You need to divide it into two separate parts.

First the part where he accelerates. Find the distance covered while he accelerates : 2as=v^2-u^2 ; s = (10^2)/2×2.5 =20m. Now find the time during this acceleration : s = ut+1/2at^2 ; t^2 = 16 therefore t = 4s.

Now the second part. We need to find the time taken when we moves at a constant speed of 10. Distance is 100-20 = 80m ,
t = distance/speed ; 80/10 = 8s

Now find the total time 8+4 = 12s. The answer is C.
 
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You need to divide it into two separate parts.

First the part where he accelerates. Find the distance covered while he accelerates : 2as=v^2-u^2 ; s = (10^2)/2×2.5 =20m. Now find the time during this acceleration : s = ut+1/2at^2 ; t^2 = 16 therefore t = 4s.

Now the second part. We need to find the time taken when we moves at a constant speed of 10. Distance is 100-20 = 80m ,
t = distance/speed ; 80/10 = 8s

Now find the total time 8+4 = 12s. The answer is C.
Jazak Allah!!! I was finding the solution since hourssss
 
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This question involves the concept of projectile motion. You know that whenever there's a force acting on a body, the body accelerates. For a projectile in the absense of air, the horizontal velocity is constant. Since the velocity is constant, it means that there is no acceleration. No acceleration means, no force. So there is no force horizontally on the projectile.

Now moving to the vertical motion. On moon, there's a force of gravity which pulls the projectile down. This force of gravity is constant.

So the answer is C.
 
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This question involves the concept of projectile motion. You know that whenever there's a force acting on a body, the body accelerates. For a projectile in the absense of air, the horizontal velocity is constant. Since the velocity is constant, it means that there is no acceleration. No acceleration means, no force. So there is no force horizontally on the projectile.

Now moving to the vertical motion. On moon, there's a force of gravity which pulls the projectile down. This force of gravity is constant.

So the answer is C.
THANKYOU! unfortunately, I was not aware of this concept.
 
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