Question

What is the ratio between the initial and final kinetic energies of a car, if its velocity is increased by four times?

1:8
1:7
1:16

Answer 1

Let initial velocity be v

So

initial kinetic energy

• KE=1/2mv²

Final velocity is four times v i.e 4v

Final kinetic energy

• KE=1/2m(4v)²
• KE=1/2m(16v²)

Find ratio

• 1/2m(16v²):1/2mv²
• 16v²:v²
• 16:1

Or

• 1:16

Option C

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