## Physics: Principles with Applications (7th Edition)

a. $9.06 \times 10^5 J$ b. $9.06 \times 10^5 J$ c. Yes.
a. Find the change in gravitational PE. $$\Delta PE = mgy_f-mgy_i=mg(y_f-y_i) = (66.5 kg)(9.80 \frac{m}{s^2})(1390 m)=9.06 \times 10^5 J$$ b. This is the minimum work required. c. The actual work is almost certainly greater than this because the hiker must overcome resistive forces and inefficiencies.