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Grade 11Mechanics

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Q.A particle moves from rest at A on the surface of a smooth cylinder of radius r as shown.At B it leaves the cylinder.The equation relating alpha and beta is

a.)3sin(alpha)=2cos(beta)

b.)2sin(alpha)=3cos(beta)

c.) 3sin(beta)=2cos(alpha)

d.)2sin(beta)=3cos(alpha)

Profile image of Raj Deol
15 Years agoGrade 11
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1 Answer

Profile image of vikas askiitian expert
15 Years ago

let the horizonta lsurface of sphere is at zero potential....radius of sphere os R...

at point A ,

     KE is 0 ,PE =mgRcos(alpha)

at point B

 KE=mv2 /2 , PE=mgRsin(beta)

applying conservation of energy

 total energy initial = total energy final

 mv2 /2 = mgR{cos(alpha)- sin(beta)}................1

on resolving weight in two components will give one in direction opposite to normal reaction at point B...

so we can say that centripital force is provided by wsin(beta) only because normal reaction is 0 at this point as the body loses contact....

        wsin(beta)=mgsin(beta)=mv2 /R...............2

 on solving 1 and 2 we get

     3sin(beta)=2cos(alpha)

hence option c is correct....