height

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a ball of mass m is thrown up with a vel. 10 m/s.and it returns to the hand of the thrower with a vel .of 9 m/s. find the height attained by the ball(take level of hand to be 0 and air resistance to be uniform)

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2 Answers

Ankur Jay ·2010-01-04 23:58:56

Here u just have to use the formula H = U²/ 2(g+a) for going up, and H = U²/2(g-a) for going down, where a is acceleration due to air resistance.

As the ball moves up, it experiences a retardation due to g, as well as air resistance hence, g+a.
As the ball moves down, air resistance pushes it up while g pushes it down hence g-a.

So we get,

1002(10 + a) = 812(10-a)

Hence we get a = 190/181.

Putting this in the equation H = 100/2(g+a) we get,

H = 50 x 812000

H = 4.525 m.