Physics - Playground Slide?

Question

A 20.0 kg child slides down a 4.00 m-high playground slide. She starts from rest, and her speed at the bottom is 2.10 m/s.

What is the change in the thermal energy of the slide and the seat of her pants (in Joules)?

Answer 1

The potential energy decrease when the child slides down:
P = mgh = (20.0kg)*(9.8m/s^2)*(4.00m) (in J)
Her final kinetic energy is:
K = 0.5*mv^2 = 0.5*(20.0kg)*(2.10m/s)^2 (also in J)
Based on energy conservation, the difference between the P and K is the heat released:
H = P - K
Please do the math.