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2. motion in straight line — Physics STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 SciencePhysics2. motion in straight line1 Mark
MCQ
A body is projected vertically up with a velocity $v$ and after some time it returns to the point from which it was projected. The average velocity and average speed of the body for the total time of flight are
  • A
    $\vec v/2\,$and $v/2$
  • ✓
    $0$ and $v/2$
  • C
    $0$ and $0$
  • D
    $\vec v/2$ and $0$
✓

Answer

Correct option: B.
$0$ and $v/2$
b
(b) Average velocity $=0$ because net displacement of the body is zero.

Average speed $ = \frac{{{\rm{Total \,distance \,covered }}}}{{{\rm{Time \,of\, flight}}}}$$ = \frac{{2{H_{\max }}}}{{2u/g}}$

==> ${v_{av}} = \frac{{2{u^2}/2g}}{{2u/g}}$ ==> ${v_{av}} = u/2$

Velocity of projection $= v$ (given)

$\therefore $ ${v_{{\rm{av}}}} = v/2$

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