MCQ
A particle moves in the $x-y$ plane under the action of a force $\overrightarrow F $ such that the value of its linear momentum $(\overrightarrow P )$ at anytime t is ${P_x} = 2\cos t,\,{p_y} = 2\sin t.$ The angle $\theta $between $\overrightarrow F $ and $\overrightarrow P $ at a given time $t$. will be $\theta =$ ........... $^o$
  • A
    $0$
  • B
    $30$
  • $90$
  • D
    $180$

Answer

Correct option: C.
$90$
c
(c) ${P_x} = 2\cos t$, ${P_y} = 2\sin t$ $⇒$$\vec P = 2\cos t\;\hat i + 2\sin t\;\hat j$

$\vec F = \frac{{d\vec P}}{{dt}} = - 2\sin t\;\hat i + 2\cos t\;\hat j$

$\vec F.\vec P = 0$  $⇒$ $\theta = 90^\circ $

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