RRB Group D 15-Sep-2018 Shift 1 Solved Paper

Question : 75 of 100

Marks: +1, -0

Two objects A and

{B}

are moving with the same velocity. The mass of object A is twice that of B. The ratio of the kinetic energy of A to that of

{B},( {K}_{ {A}} / {K}_{ {B}})

will be

Solution:

Let mass of ball A be '2m' and mass of ball B be 'm' - - - -(given).
Now, since

{KE}=1 \/ 2 {mv}^{2}

Therefore,

{KE}

of object

{A}

=1 \/ 2(2 {m})( {v})^{2}

And

{KE}

of object

{B}=1 \/ 2( {m})( {v})^{2}

Now, ratio of KE's of both objects,

⇒ \;\; ( {KE}

{A}) \/( {KE}

{B})

⇒[1 \/ 2(2 {m})( {v})^{2}] \/[1 \/ 2( {m})( {v})^{2}]

⇒ 2 \/ 1

Therefore, ratio of

{KE}

of object A to ball

{B}

is 2: 1 (answer)

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