The kinetic energy of a body is ‘K’. If one-fourth of its mass is removed and velocity is doubled, the new kinetic energy will be _____

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Editor">Editor Staff asked 1 year ago

The kinetic energy of a body is ‘K’. If one-fourth of its mass is removed and velocity is doubled, the new kinetic energy will be _____
 
(a) K
 
(b) 3K
 
(c) 4K
 
(d) 9K/4
 
I have been asked this question in a national level competition.
 
This question is from Kinetic Energy topic in division Work, Energy and Power of Physics – Class 11
Select the correct answer from above options 
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Editor">Editor Staff answered 1 year ago

Right option is (b) 3K
 
The best explanation: K = 1/2 x m x v^2
 
New kinetic energy (K’) = 1/2 x m’ x v’^2
 
m’ = 3m/4; [one-fourth of mass is removed]
 
v’ = 2v; [velocity is doubled]
 
K’ = 1/2 x (3m/4) x (2v) ^2
 
 = 1/2 x m x v x 3
 
 = 3 x K
 
 = 3K.

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