Question

A weight is suspended by a string and pulled by a force so that the string is deflected through a given angle.The pulling force will be a minimum when it is
A)horizontal
B)inclined at 45 degree to the string
C)perpendicular to the string
D)vertical

Answer 1

$$\begin{gathered} \sin cetheweightissuspendedandpulledbyaforcesothatstringisdeflected \\ thepullingforceisgivenby \\ F=mg\sin \theta \\ whenthestringisverticalthentheanglewillbe0 \\ sotheforcebecomezero,therefore \\ whenthestringisverticaltheforcewillbeminimum,soDistheoption. \end{gathered}$$