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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
Two putty balls of equal mass moving with equal velocity in mutually perpendicular directions, stick together after collision. If the balls were initially moving with a velocity of $45\sqrt 2 \,m{s^{ - 1}}$ each, the velocity of their combined mass after collision is .................. $\mathrm{m} / \mathrm{s}^{-1}$
  • A
    $45\sqrt 2$
  • ✓
    $45$
  • C
    $90$
  • D
    $22.5\sqrt 2$
✓

Answer

Correct option: B.
$45$
b
(b)Initial momentum
$\vec P = m45\sqrt 2 \;\hat i + m45\sqrt 2 \;\hat j$ $⇒$ $|\vec P| = m \times 90$
Final momentum $2m \times V$
By conservation of momentum $2m \times V = m \times 90$
$V = 45\,m/s$

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