NTSE Stage 2 SAT 2018 Exam Question Paper

Question : 34 of 100

Marks: +1, -0

Three balls A, B and C of same size but of different masses, are thrown with the same speed from the roof of a building, as shown in figure. Let

v_A,v_B

and

v_C

be the respective speeds with which the balls A, B, and C hit the ground. Neglecting air resistance, which one of the following relations is correct?

Solution:

Let u is the initial velocity at height H.
By conservation of Mechanical energy.

For ball A:

\;\;{1}/{2}mu^{2}+mgh=\;\;{1}/{2}mv_{A}^{2}→{V}_{{A}}=√{u^{2}+2gH}

For ball B

;\;\;{1}/{2}mu^{2}+mgh=\;\;{1}/{2}mv_{B}^{2}⇒{V}_{{B}}=√{u^{2}+2gH}

For ball C:

\;\;{1}/{2}mu^{2}+mgh=\;\;{1}/{2}mv_{C}^{2}⇒{V}_{{C}}=√{u^{2}+2gH}

Clearly

V_A=V_B=V_C

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