Question

an object has initial velocity u. Later it's velocity becomes double, what will
happen to its KE, will it increase or
decrease ? Hence find ratio of the
final and initial KE.​

Answer 1

Explanation:

Let,

mass of object = m, Initial velocity = u

Kinetic energy = $\small{\frac{1}{2}*m*u^2}$

Then,

Final velocity = 2 * inti. velo. = 2*u = 2u

Kinetic energy = $\small{\frac{1}{2}*m*(2u)^2}$

Therefore,

As $\small{\frac{1}{2}*m*(2u)^2}$ is $\small{2^2*\bold{\frac{1}{2}*m*(u)^2}}$ , it is more than the initial one.

Required ratio:

= > $\small{\frac{\frac{1}{2}*m*u^2}{\frac{1}{2}*m*(2u)^2}}$

= > $\small{\frac{u^2}{4u^2}=\frac{1}{4}}$

Required ratio is 1:4