A body of mass $m$ hangs at one end of a string of length $l$, the other end of which is fixed. It is given a horizontal velocity so that the string would just reach where it makes an angle of $60^o$ with the vertical. The tension in the string at mean position is
$2\,mg$
$mg$
$3\,mg$
$\sqrt3\, mg$
Two persons are holding a rope of negligible weight tightly at its ends so that it is horizontal. A $15\, kg$ weight is attached to the rope at the mid-point, which now no longer remains horizontal. The minimum tension required to completely straighten the rope is
Two masses $M$ and $m$ are connected by a weightless string. They are pulled by a force $F$ on a frictionless horizontal surface., the acceleration of mass $m$ is
A false balance has equal arms. An object weigh $X$ when placed in one pan and $Y$ when placed in other pan, then the weight $W$ of the object is equal to
What is Free body diagram ?