Question

A 75-kg person, starting from rest, sleds down a slide 40. m high hill reaching the bottom with a speed of 18 m/s. Calculate

a) the PE at the top,

b) the KE at the bottom of the hill,

c) and finally, the thermal energy that was generated in the process.

Answer 1

(a)

the PE at the top,

$= mgh \\ = 75 \times 10 \times 40 \\ = 75 \times 400 \\ = 30000 \\ 30 \: kj$

(b)

the KE at the bottom of the hill,

$= \frac{1}{2} m {v}^{2} \\ = \frac{1}{2} \times 75 \times {18}^{2} \\ = 12150 \\ = 12.15 \: kj$