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halosh92:

--- Quote from: Phosu on May 07, 2010, 08:36:28 pm ---could you plz explain the difference between speed of approach and speed of seperation. how do we know that they are same?
wen and how can we use this formula? and why cant we just use m1u1+m2u2=m1v1+m2v2

plus wen u solve the ans u've given, it gives uA+uB=vA+vB but the mark scheme says its uA+uB=vA-vB

i got till the total current part, but why did u take the resistance as 5 in the next step?

Thanks alot for solving :)

--- End quote ---

because the resistor is between the terminal look at the second loo[, and view the resistor as a single component in a battery..........nid will explain q11 better than me
np POSH  ;D ;D ;D

nid404:
Q11) this is gonna be long...

In an elastic collision...momentum as well as kinetic energy is conserved,,
conservation of momentum
total momentum before collision=total momentum after collision.
mu1+mu2=mv1+mv2

conservation of k.e
1/2mu12+ 1/2mu22= 1/2mv12+1/2mv22

cancel all the halfs first, then cancel all the 'm' terms.

in steps...here's how u do it

m(u1-v1)=m(v2-u2) 1)
m(u12-v12)= m( v22-u22)  2)

since (u12-v12)= (u1-v1)(u1+v1)
     &  ( v22-u22)=(v2-u2)(v2+u2)   

divide the 2nd eqn by the first
m(u12-v12)      m( v22-u22)
---------------------------------= ------------------------------------
m(u1-v1)                                                   m(v2-u2)

m [(u1-v1)(u1+v1)]=[m(v2-u2)(v2+u2)]
-------------------  ------------------
m(u1-v1)                  m(v2-u2)

and then cancelling gives
(u1+v1)=(v2+u2)
or
u1-u2=v2-v1

now coming back to the question.
u1-u2 in this case will be positive because u for the other body is in the opp direction
u1-(-u2)=u1+u2
v2-v1 will be as it...both move in the same direction after collision
so u1+u2=v2-v1

that was tiring....i really hope you got it

Phosu:
thank you soo much for that,
it was really helpful! :)

astarmathsandphysics:
Thanks too. Really gratelul cos I had to recover a hard disk during exam season - forced to be absent for 2 days

nid404:
pleasure is all mine  ;D

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