IIT JEE , AIEEE Forum - Physics , Mechanics - please explain the role of friction in case of rolling

anchitsaini

we don't need to consider the behaviour of friction here as the shell will roll from the moment it is hit and not slip --

a = acceleration = F / m --------1

also for rolling a = r

-----------2

also ,

= I

F ( h - r) = 2 m r²

/ 3
where h is the height from the ground where the cue is hit

this gives

= 3 F ( h - r ) / 2 m r ²

equating 1 and 2

F / m = 3 F ( h - r ) / 2 m r

hence --

h - r = 2/3 r

thus it should be hit at a height of 2/3 r from centre or 5/3 r from the ground

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