I do not know how to start this problem. I think the answer isE, but i am not su

Question

I do not know how to start this problem. I think the answer isE, but i am not sure. here is the problem: A rock is dropped from rest from a height h above theground. it falls and hits the ground at 11m/s. From what heightshould the rock be dropped so that its speed on hitting the groundis 22m/s? Neglect air resistance. a) 0.71h b) 3.0h c) 4.0h d)1.4h e)2.0h I do not know how to start this problem. I think the answer isE, but i am not sure. here is the problem: A rock is dropped from rest from a height h above theground. it falls and hits the ground at 11m/s. From what heightshould the rock be dropped so that its speed on hitting the groundis 22m/s? Neglect air resistance. a) 0.71h b) 3.0h c) 4.0h d)1.4h e)2.0h

Explanation / Answer

given final velocity of h1 height is v1=11m/s final velocity of h2 height is v2 =22m/s from the kinematic equation = v2 - u2 =2ah here u = 0 v2 = 2ah v2 h v12 h1 v22 h2 then v12/v22 =h1/h2 h2 = h1(v22/v12)       = here h1 = h then h2 = h(22/11)2         h2 = 4.0h so c is correct answer.

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