Question

A bullet losses 19% of it's kinetic energy when passes through an obstacle the percentage change in it's velocity is?
Reduced by 10%
Reduced by 19%
Reduced by 9.5%
Reduced by 11%
​

Answer 1

Explanation:

Let initial kinetic energy be 100 J

i.e, 1/2 (mv²) = 100,Where m is mass and v is the velocity of that bullet

Or mv²= 200

Or v=√(200/m)......(1)

But given that bullet losses it's kinetic energy by 19% , therefore final kinetic energy will be 100-19= 81 J

Now kinetic energy become (say) 1/2 (mv'²) =81

, where v' is the changed velocity due to which kinetic energy has changed.

Or mv'²= 162

Or v' = √(162/m).......(2)

from (1) & (2)

Total percentage change in its velocity

=( V - V') / V multiplied with 100

=[ {√(200)-√(162)} ÷√(200) ] *100=100/10 = 10%

Hence change in it's velocity whould be reduced by 10%. <= Ans.

I hope,It was helpful to you.