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

Gujarat BoardEnglish MediumSTD 11 SciencePhysics5.work,energy,power and collision1 Mark
MCQ
A truck moving on horizontal road towards east with velocity $20\, ms^{-1}$ collides elastically with a light ball moving with velocity $25\, ms^{-1}$ along west. The velocity of the ball just after collision
  • ✓
    $65\, ms^{-1}$ towards east
  • B
    $25\, ms^{-1}$ towards west
  • C
    $65\, ms^{-1}$ towards west
  • D
    $20\, ms^{-1}$ towards east
✓

Answer

Correct option: A.
$65\, ms^{-1}$ towards east
a
Taking east as positive direction.

velocity of approach $=25-(-20)=45 m / s$

velocity of separation $=v-20$

elastic collision, e $=1,$ velocity of approach = velocity of separation

$v-20=45$

$v=65 \mathrm{m} / \mathrm{s}$

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