Search any question & find its solution
Question:
Answered & Verified by Expert
A force $\overrightarrow{\mathrm{F}}=4 \hat{\mathrm{i}}-15 \hat{\mathrm{j}} \mathrm{N}$, acts on a body resulting in a displacement of $6 \hat{i}$. If the body had a kinetic energy of 7 joules at the beginning of the displacement, the kinetic energy at the end of the displacement is
Options:
Solution:
2657 Upvotes
Verified Answer
The correct answer is:
$31 \mathrm{~J}$
Work done $=\overrightarrow{\mathrm{F}} \cdot \overrightarrow{\mathrm{S}}$
$\begin{aligned} & \Rightarrow \quad \Delta \mathrm{K}=\overrightarrow{\mathrm{F}} \cdot \overrightarrow{\mathrm{S}} \\ & \Rightarrow \quad \mathrm{K}_{\mathrm{f}}-7=(4 \hat{\mathrm{i}}-15 \hat{\mathrm{j}}) \cdot(6 \hat{\mathrm{i}}) \Rightarrow \mathrm{K}_{\mathrm{f}}-7=24 \Rightarrow \mathrm{K}_{\mathrm{f}}=31 \mathrm{~J}\end{aligned}$
$\begin{aligned} & \Rightarrow \quad \Delta \mathrm{K}=\overrightarrow{\mathrm{F}} \cdot \overrightarrow{\mathrm{S}} \\ & \Rightarrow \quad \mathrm{K}_{\mathrm{f}}-7=(4 \hat{\mathrm{i}}-15 \hat{\mathrm{j}}) \cdot(6 \hat{\mathrm{i}}) \Rightarrow \mathrm{K}_{\mathrm{f}}-7=24 \Rightarrow \mathrm{K}_{\mathrm{f}}=31 \mathrm{~J}\end{aligned}$
Looking for more such questions to practice?
Download the MARKS App - The ultimate prep app for IIT JEE & NEET with chapter-wise PYQs, revision notes, formula sheets, custom tests & much more.