A stone at the end of 1m long string is whirled in a vertical circle at a constant speed of 4ms^-1. The tension in the string is 6N when the stone is

A stone at the end of 1m long string is whirled in a vertical circle a

1.	A stone at the end of 1m long string is whirled in a vertical circle at a constant speed of 4ms^-1. The tension in the string is 6N when the stone is
Answer» (a) `10ms^-1` (b) `5sqrt3ms^-1` (c) `10sqrt3ms^-1` (d) `20ms^-1` Solution :`m=1kgimpliesL=10/3m` `(T_(max))/(T_(min))=4` (i) and `V_L=sqrt(V_H^2+4gL)` Tension at highest point, `T_(min)=(mv_H^2)/(K)-MG` Tension at lowest point, `T_(max)=mv_L^2//L+mg=(m(v_H^2+4gL))/(L)+mg` Now EQ. (i) can be WRITTEN as `m[(v_H^2+4gL)/(L)+g]=4xxm((v_H^2)/(L)-g)` `implies v_H=sqrt(3gL)=10ms^-1`