Find kinetic energy! please help!?

Question

Suppose an automobile has a kinetic energy
of 2900 J.
When it moves with three times the speed,
what will be its kinetic energy?
Answer in units of J

Answer 1

Given that automobile has a kinetic energy 2900 J.

We have formula for kinetic energy K = 1/2 mv^2

K proportional v^2 (m =constant)

(K2 / K1) = (v2^2 / v1^2)

K2 = K1 * (v2^2 / v1^2)

Given that speed increased to three times v2 = 3v1

= 2900 * ( ((3v1)^2) / v1^2)

= 2900 * 9

= 26100 J