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5.work,energy,power and collision — Physics STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 SciencePhysics5.work,energy,power and collision1 Mark
MCQ
A particle which is experiencing a force, given by $\vec F = 3\vec i -12\vec j$, undergoes a displacement of $\vec d = 4\vec i$ . If the particle had a kinetic energy of $3\, J$ at the beginning of the displacement, what is its kinetic energy at the end of the displacement?
  • A
    $9\, J$
  • B
    $12\, K$
  • C
    $10\, J$
  • ✓
    $15\, J$
✓

Answer

Correct option: D.
$15\, J$
d
$\begin{array}{l}
K.E.\, - 3 = \overrightarrow F .\overrightarrow d \\
K.E. = 3 + \left( {3\hat i - 12\hat j} \right) \times \left( {4\hat i} \right)\\
K.E. = 3 + 12 = 15\,J
\end{array}$

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