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Reynold's Number

A boy sitting...

Question

A boy sitting in the rear end of the train, running at a constant acceleration on rails,throw a ball towards the fore end of the compartment with a velocity of 20m/s at angle of 37⁰ above the horizontal, when the train is running at speed of 10m/s. If the same boy catches the ball without moving from his seat and at the same height of projection, Find the speed of the train at the instant of his catching the ball.

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Solution

$h e i g h t a t t a i n b y t h e b a l l y c o m p o n e n t o f t h e v e l o c i t y = 20 \sin 37 = 12 m / s t i m e t a k e n b y b a l l = \frac{2 u \sin 37}{g} = 2 (\frac{12}{10}) = 2.4 s e c x c o m p o n e n t o f t h e v e l o c i t y = 20 \cos 37 t h i s b e c o m e s z e r o i n 2.4 s e c l e t t h e a c c n o f t r a i n b e a a = \frac{0 - 20 \cos 37}{2.4} = \frac{16}{2.4} = - 6.67 - v e f o r p s e u d o f o r c e . a c c n o f t r a i n i s 6.67 m / s^{2} s p e e d o f t r a i n w h e n h e c a t c h t h e b a l l = 10 + 6.67 * 2.4 = 26 m R e g a r d s$

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