Qualification > Math

Mechanics Question

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Dania:
Help me, Asif :)

S.M.A.T:
Here Dani :D

Dania:
Thank You, Asif. :) You help me so much.

I have another question. Take a look at the attached file, thanks :)

P.S Don't bother yourself answering (i) for me. I'm only interested in (ii), but you'll have to do the whole question to effectively help me out.

nid404:
The frictional force provides forward acceleration since there is no more tension(once block B is on the ground)

S.M.A.T:

--- Quote from: Garfield on October 14, 2010, 06:15:12 pm ---The frictional force provides forward acceleration since there is no more tension(once block B is on the ground)

--- End quote ---
Garfield u are wrong  ::).....frictional force is an opposing force so it always try to decelerate an object :)

When particle B is about to hit the floor the speed of A is also 3.95ms^-2,this is because the acceleration of A&B are same before B hit the ground and they both travel the same distance(1.3m).
Once particle B is on the ground the tension in the string become zero and the only force acting on A is frictional force and it is decelerating particle A.
therefore

u=3.95ms^-1

frictional force=ma
-0.06g=0.2a
a=-0.3g
s=2.1-1.3=0.8m(1.3m is already travelled by A when B was about to hit the ground)

(v^2)=(u^2)+2as
(v^2)=(3.95^2)+(2*-0.3g*0.8 )
v=3.29

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