JEE Main & Advanced Physics Work, Energy, Power & Collision / कार्य, ऊर्जा और शक्ति JEE PYQ - Work Energy Power and Collision

A particle gets displaced by \[\Delta \overline{r}=\left( 2\hat{i}+3\hat{j}+4\hat{k} \right)m\] under the action of a force \[\vec{F}=\left( 7\hat{i}+4\hat{j}+3\hat{k} \right).\] The change in its kinetic energy is [JEE ONLINE 07-05-2012]

A) 38 J

B) 70J

C) 52.5 J

D) 126 J

Correct Answer: A

Solution :

[a] According to work-energy theorem, Change in kinetic energy = work done

\[=\vec{F}.\Delta \vec{r}=\left( 7\hat{i}+4\hat{j}+3\hat{k} \right).\left( 2\hat{i}+3\hat{j}+4\hat{k} \right)\]

\[=14+12+12=38J\]