• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

Physics: Post your doubts here!

D

darknessinme

Messages
55
Reaction score
32
Points
28
farhan143 said:
My doubts in the following questions
can u please explain it to me...
View attachment 4548
Click to expand...

Q13 Think about which way the lever would turn with the forces. 5N and 10N turns the lever anti clockwise and 20N turns it clockwise.
Total moments= a.c.w moments + c.w moments. They are in opposite directions, so signs are different.
Total moments=(5Nx2m + 10Nx2m)+-(20Nx3m)=-30Nm. A is answer.

Q16 Power is rate at which work is done. The gradient will give this. Basically the question is asking when gradient(power) is maximum. This is during the period of 2-3s so the gradient from that is 30W, so answer is C.

Q34 Just note that resistance is the ratio of Voltage to current, so Voltage/Current at any point on the graphs give R. This has nothing to do with gradients or 1/gradients which is common misconception.
Now, you should know IV graphs for components in A. This is wrong. The resistance of Q is in fact decreasing so B is wrong. At 1.5A the resistances are almost the same so C is incorrect.
At 0.5A resistance for P=4ohm and Q=8ohm. Since P=V^2/R, the Power in P=2^2/4=1W and Power in Q=4^2/8=2W so infact D is correct.
 
farhan143

farhan143

Messages
324
Reaction score
24
Points
28
thnk you soo much
i've been waiting the whole afternoon and evening for the reply to my doubts
cuz i've this test 2mrw so im kinda preparin on past papers so
thanks again
hope more of my doubts will get cleared in this thread!
:):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):) :):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):):)
 
rz123

rz123

Messages
1,833
Reaction score
587
Points
93
KurayamiKimmi said:
http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_s03_qp_1.pdf
ermm... q27 can anybody explain it ?
Click to expand...
c, the light from the lamp is not coherent. Coherent sources are those sources of light which emit continuous light waves of same wavelength , same frequency and are in same phase or have constant phase difference.
For observing interference phenomenon coherence of light waves is a must.
For light waves emitted by two sources of light , to remain coherent the initial phase difference between waves should remain constant in time. If the phase difference changes continuously or randomly with time then the sources are incoherent. Two independent sources of light are not coherent and hence can not produce interference because light beam is emitted by millions of atoms radiating independently so the phase difference between waves from such sources fluctuates randomly many times per second.
 
farhan143

farhan143

Messages
324
Reaction score
24
Points
28
I have doubt in b(i) i dont know where to draw and how??
doubt.jpg
Plzz explain me and show me ur diagram where u've drawn
THANK YOU in advance
 
farhan143

farhan143

Messages
324
Reaction score
24
Points
28
i have another doubt it is 4rm 2004 may/june paper 2 Q1_b
doubt.jpg

the drawing part is my weakness
i dont know where to draw the two lines can anyone draw the diagram and post it back thank you!
 
N

Nibz

XPRS Moderator
Messages
4,615
Reaction score
9,574
Points
523
farhan143 said:
another doubt !!!!
View attachment 4630
Click to expand...
(i) Use F = ma
a= 4.5 - 3.5/0.14 (Change in speed) / time
acceleration comes out as 57.1 ms^2
F = (35/1000) * 57.1
F = 1.998
F ~ 2 N

(ii) Loss in kinetic Energy = 1/2 * (35/1000)(4.5^2 - 3.5^2) OR Initial K.E = 1/2 * (35/1000) * 4.5^2 and Final K.E = 1/2 * (35/1000) * (3.5)^2

= 0.14J

(c) There is loss of kinetic energy; the collision of the ball with the plate is inelastic. The loss of momentum during the impact is gained by the plate. So the overall momentum is constant i.e linear momentum is conserved.
 
You must log in or register to reply here.
Top