Qualification > Sciences
Edexcel PHYSICS Doubts
wakemeup:
I'm pretty much completely lost on Q16 of Jun 10 paper 4. Would really appreciate it if someone could clearly explain parts bi, ci and cii.
Also, in Q13b, how are we supposed to estimate the radius if we don't have any reference in the diagram?
Romeesa-Chan:
Doubts:
*A 47micro F capacitor is charged to a pd of 15V and then discharged through a 100k Ohm resistor. How long does it take for half of the energy stored in the capacitor to have dissipated in the circuit?
*A beam of electrons enters a region of uniform electric field, moving at right angles to the field and is deflected into a circular path.
Draw a diagram to show the path of electrons, including directions of the electron velocity 'v' and the magnetic field 'B'.
Romeesa-Chan:
--- Quote from: wakemeup on June 20, 2011, 12:17:15 pm ---I'm pretty much completely lost on Q16 of Jun 10 paper 4. Would really appreciate it if someone could clearly explain parts bi, ci and cii.
Also, in Q13b, how are we supposed to estimate the radius if we don't have any reference in the diagram?
--- End quote ---
I am lost in 13b myself too. :(
Ok, Q16:
bi) Capacitor stores charge, as charge flows in during the charging process, pd is also formed.
If the voltage is constant, the capacitor will not discharge. The graph is during the charging process. Hence, pd is constant.
(remember: during discharging process, pd falls.)
ci) Use E= 1/2*C*V^2
(take voltage value from the graph)
cii) Compare the graph with the previous one and see the change in voltage value. (pd decreases)
Capacitor is initially charging from power supply then the capacitor is discharging exponentially.
(remember: the changing position of switches causes the discharge process, instead here. . . we added a power supply)
I hope that's clear. :)
viktress:
Hey guys could you help me out with this question I've trying to crack for almost a day now? It's from the Edexcel a2 revision guide (physics).
A runner of mass 65kg is running a circular running track at a sped of 5.0m/s. The magnitude of the runner's change in momentum from starting to end position after half a revolution is
A. 0 N s
B. 325 N s
C. 460 N s
D. 625 N s
The correct answer according to the book is D, but I just can't seem to be able to get i. Could you please try to work it out? Thanks!
Romeesa-Chan:
--- Quote from: viktress on June 20, 2011, 01:31:57 pm ---Hey guys could you help me out with this question I've trying to crack for almost a day now? It's from the Edexcel a2 revision guide (physics).
A runner of mass 65kg is running a circular running track at a sped of 5.0m/s. The magnitude of the runner's change in momentum from starting to end position after half a revolution is
A. 0 N s
B. 325 N s
C. 460 N s
D. 625 N s
The correct answer according to the book is D, but I just can't seem to be able to get i. Could you please try to work it out? Thanks!
--- End quote ---
The last option D is wrong- suppose to be 650N.
F*t= m*v => change in momentum
Think of half a circle.
at the "top" it is travelling ------->>> at p=mv = 325Ns
at the "bottom" it is travelling <<<------- at p=mv = -325Ns
Therefore the change in momentum is = 325 - (-325) = 650Ns
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