#### Answer

The amount of thermal energy created by friction is 537 J

#### Work Step by Step

The thermal energy is equal in magnitude to the work done by friction. We can use the work-energy theorem to find the work done by friction.
$KE_1+PE_1+W_f = KE_2+PE_2$
$0+mgh+W_f = \frac{1}{2}mv^2+0$
$W_f = \frac{1}{2}mv^2-mgh$
$W_f = \frac{1}{2}(30~kg)(11~m/s)^2-(30~kg)(9.80~m/s^2)(8.0~m)$
$W_f = -537~J$
The amount of thermal energy created by friction is 537 J.