4-1.Newton's Laws of Motion
hard

$m$  દળનો બોમ્બ $ v$ વેગથી $ \theta $ ખૂણે પ્રક્ષિપ્ત કરાવવામાં આવે છે.મહત્તમ ઊંચાઇએ તેના સમાન દળના બે ટુકડા થાય છે.એક ટુકડો પ્રક્ષિપ્ત બિંદુ તરફ પાછો આવે,તો બીજા ટુકડાનો વેગ કેટલો હશે?

A

$ 3v\cos \theta $

B

$ 2v\cos \theta $

C

$ \frac{3}{2}v\cos \theta $

D

$ \frac{{\sqrt 3 }}{2}v\cos \theta $

(IIT-1984)

Solution

(a)Shell is fired with velocity $v$ at an angle $\theta$ with the horizontal.
So its velocity at the highest point
$=$ horizontal component of velocity $=$$v\cos \theta $
So momentum of shell before explosion $=$ $mv\cos \theta $

When it breaks into two equal pieces and one piece retrace its path to the canon, then other part move with velocity $V.$

So momentum of two pieces after explosion
$ = \frac{m}{2}( – v\cos \theta ) + \frac{m}{2}V$
By the law of conservation of momentum
$mv\cos \theta = \frac{{ – m}}{2}v\cos \theta + \frac{m}{2}V$==> $V = 3v\cos \theta $

Standard 11
Physics

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