Q125 / 180 · KCET 2015 · Physics
The kinetic energy of a body of mass \( 4 \mathrm{~kg} \) and momentum \( 6 \mathrm{Ns} \) will be
- A\( 2.5 \mathrm{~J} \)
- B\( 3.5 \mathrm{~J} \)
- Correct answerC\( 4.5 \mathrm{~J} \)
- D\( 5.5 \mathrm{~J} \)
Solution
Given, mass, \( m=4 \mathrm{~kg} ; \) momentum, \( m v=6 \mathrm{~N} \mathrm{~s} \)
Therefore, kinetic energy
\( =\frac{1}{2} m v^{2}=\frac{1}{2} \frac{(m v)^{2}}{m}=\frac{6 \times 6}{2 \times 4}=\frac{36}{8}=4.5 \mathrm{~J} \)
Thus, kinetic energy of body \( =4.5 \mathrm{~J} \)
Therefore, kinetic energy
\( =\frac{1}{2} m v^{2}=\frac{1}{2} \frac{(m v)^{2}}{m}=\frac{6 \times 6}{2 \times 4}=\frac{36}{8}=4.5 \mathrm{~J} \)
Thus, kinetic energy of body \( =4.5 \mathrm{~J} \)
Hence, the correct answer is option: 'C'.