A stone of mass `0.3g` is tied to one end of string `0.8m` long and rotated in a vertical circle At what speed of the stone will the tension in the string be zero at the highest point of the circle ? What will be the tesion at the lowest point in this case ? Take `g = 980 cm^(-2)` .

Answer

`2.8 m//s ; T = 17.64 N` .

Explanation

Here, `m = 0.3 kg , r = 0.8 m, upsilon = ? , T = ?`
When tension in the string is zero at the highest point speed of stone at the highest point is
`upsilon_(H) = sqrt(gr) = sqrt(9.8 xx 0.8) = 2.8m//s`
As `T_(L) -T_(H) = 6 mg`, and `T_(H) = 0`
`T_(L) = 6mg = 6 xx 0.3 xx 9.8 = 17.64 N` .