## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (3rd Edition)

We can write an expression for the kinetic energy when the speed is $v$: $KE_1 = \frac{1}{2}mv^2$ We can write an expression for the kinetic energy when the speed is $3v$: $KE_2 = \frac{1}{2}m(3v)^2$ $KE_2 = 9\times ~\frac{1}{2}mv^2$ $KE_2 = 9\times ~KE_1$ The particle's kinetic energy increases by a factor of 9.