A) \[90{}^\circ \]
B) \[0{}^\circ \]
C) \[180{}^\circ \]
D) \[30{}^\circ \]
Correct Answer: A
Solution :
[a] \[P=\sqrt{P_{x}^{2}+P_{y}^{2}}=\sqrt{{{(2\,\cos t)}^{2}}+{{(2\,\sin t)}^{2}}}=2\] If m is the mass of the body, then kinetic energy \[=\frac{{{P}^{2}}}{2m}=\frac{{{(2)}^{2}}}{2m}=\frac{2}{m}\] Since kinetic energy does not change with time, both work done and power are zero. Now, power \[=Fv\,\cos \theta =0\] As \[F\ne 0,v\ne 0\] \[\therefore \] \[\cos \theta =0\] or \[\theta =90{}^\circ \] As direction of \[\vec{p}\] is same that of \[\vec{v},\] \[(\because \overrightarrow{P}=m\overrightarrow{v}),\] hence angle between \[\overrightarrow{F}\] and \[\overrightarrow{P}\] is equal to \[90{}^\circ \].You need to login to perform this action.
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