Q1. A particle moves in $x - y$ plane under the influence of a force $\vec { F }$ such that its linear momentum is $\overrightarrow { \mathrm { p } } ( \mathrm { t } ) = \hat { i } \cos ( \mathrm { kt } ) - \hat { j } \sin ( \mathrm { kt } )$. If k is constant, the angle between $\overrightarrow { \mathrm { F } }$ and $\overrightarrow { \mathrm { p } }$ will be :\\
(1) $\frac { \pi } { 4 }$\\
(2) $\frac { \pi } { 6 }$\\
(3) $\frac { \pi } { 2 }$\\
(4) $\frac { \pi } { 3 }$