ALL CIE PHYSICS DOUBTS HERE !!!

[aneeta]

it is written ari oct-nov
so winter afcos  
will get to it soon

Exactly what he said:p OCTOBER/NOVEMBER 2007 QUESTION 4C

[EMO123]

here is the answer with method
stress = force / area
make area subject of the formula
so that will be area=force/stress
area(mini) = (1.9*10³) / (9.5*10⁸)
= 2.0*10^–6 m²
as it is stretched so the max-mini
area (max)= (3.2 – 2.0)*10^–6
= 1.2*10^–6 m²
so mini area=2.0*10^-6m²
and max area=1.2*10^-6m²

[yasser37]

Hi guys
Paper 5
June 07
Question 2
The error bars are horizontal yet too small to be drawn
can someone attach a drawing? Thanks

[aneeta]

June 08 paper 2 question 6(b)

[NidZ- Hero]

can someone explain the difference between stationary waves and progressive waves

[EMO123]

June 08 paper 2 question 6(b)

6 (b) 1st is open so power supply so that is zero
        2nd from the first the power is supplied so it will move to s₂ but s₃ is closed so it will not move from s₃
              so only of s₂ which is 1.5kW so for second it is 1.5kW
        3rd the power is supplied from s₂ and s₃ so both are added 1.5kW+1.5kW=3kW
        4th - Current flows through A and B (not the part of the junction with S₂ as it has infinite resistance)
                R = 38.4ohms, V one heater receives is 120V , P =  V²/R = 120²/38.4 = 375W
                Thus, for two heaters = 375*2 = 750W or 0.75kW
        5th - Current flows through all heaters. Power in A and B as calculated previously = 0.75kW
                Power in C = V²/R = 240²/38.4 = 1.5kW Total - 1.5 + 0.75 = 2.25kW

[EMO123]

can someone explain the difference between stationary waves and progressive waves

The notes we hear from a cello are created by the vibrations of strings. The wave patterns on the vibrating strings are called stationary waves.

The waves in the air which carry the sound to our ears transfer energy, and so are called progressive waves.

Hope it helps.

[NidZ- Hero]

The notes we hear from a cello are created by the vibrations of strings. The wave patterns on the vibrating strings are called stationary waves.

The waves in the air which carry the sound to our ears transfer energy, and so are called progressive waves.

Hope it helps.

 

But in my book there is this part which i dont understand the amplitude of the vibration varies with position along the string: its zero at the nodes and maximum at an antinode .in progressive waves all the points have the same amplitude

[Ghost Of Highbury]

But in my book there is this part which i dont understand the amplitude of the vibration varies with position along the string: its zero at the nodes and maximum at an antinode .in progressive waves all the points have the same amplitude

Yes, u see, the stationary waves are made out of 2 waves traveling in opposite directions. The phase difference is 180^o, and because of the superposition of the 2 waves, the resultant displacement at the nodes is 0 and is maximum at the antinodes.

[aneeta]

A hard ball and a soft ball, with equal masses and volumes are thrown at a glass window. The balls hit the window at the same speed. Suggest why the hard ball is more is more likely than the soft ball to break the window.

[Ghost Of Highbury]

A hard ball and a soft ball, with equal masses and volumes are thrown at a glass window. The balls hit the window at the same speed. Suggest why the hard ball is more is more likely than the soft ball to break the window.

Newton's second law of motion. Force is the rate of change of momentum. F = Change in momentum / t

The ball which exerts more force on the window is, obviously, more likely to break the window.

The change in momentum is the same as the mass and velocity is the same for both the balls.

ALthough, the time the balls are in contact with the window is greater in the soft one than the hard one (deformation)

An increase in time, means decrease in Force. Hence, hard ball is more likely to break the window.

PS : Does anybody know how to put the 'delta' sign here? (Yes, the triangle symbol, Ari? )

[TJ-56]

A hard ball and a soft ball, with equal masses and volumes are thrown at a glass window. The balls hit the window at the same speed. Suggest why the hard ball is more is more likely than the soft ball to break the window.

Force = rate of change of momentum = mv\t
So the masses and the velocities are equal. So the different variable here is the time t.
Soft ball: the ball gets compressed more and hence is more in contact with the window than the hard ball. Thus, momentum is much less and so it doesn't break the window. The hard ball has negligable compression and hence has a high momentum, breaking the window.

[TJ-56]

Can someone explain October/November 2010 Paper 54 question 2 (e)? The mark scheme is useless on this one.
Thanx in advance.

[aneeta]

May/June 2005 paper 2 question 6b(iii)
I don't get why it's sin and not cos, or is it cos I didn't do part (i) correctly? :s

[Arthur Bon Zavi]

Newton's second law of motion. Force is the rate of change of momentum. F = Change in momentum / t

The ball which exerts more force on the window is, obviously, more likely to break the window.

The change in momentum is the same as the mass and velocity is the same for both the balls.

ALthough, the time the balls are in contact with the window is greater in the soft one than the hard one (deformation)

An increase in time, means decrease in Force. Hence, hard ball is more likely to break the window.

PS : Does anybody know how to put the 'delta' sign here? (Yes, the triangle symbol, Ari? )

See the code.