Peter, a student was humiliating himself on the ski slopes. So, he decided to take a break in the lodge. Peter was so discouraged that he turned to his physics teacher for help in skiing.
Dr. Miller, the professor, was very keen on seeing daily lives as physics problems. So, the professor wanted Peter to prove that skiing dealt with conservative forces.
Dr. Miller said, "My mass is exactly 80kg. If I started from rest at the top of the slope and skied down the slope (total elevation = 110m) and you clocked my speed at 20m/s at the bottom of the slope, would this system be conservative?
What is the answer to the professor's question? Explain your answer with valid reasoning.
(In reply to
solution (sort of) by Charlie)
This is correct - most of the energy goes to friction w/ the ground and air. There is a chemical energy too; his breakfast goes to his muscles and body heat. But, there was a arithmetic error in the Kinetic Energy result - it is twice as large: 16,000 J, so that about 4/5th of the PE was lost, not 9/10th).
If the system were summed closed, then all energy (and all momentum, force, and mass, for that matter) would be conserved - a bit hard to do in practice.
re: solution (sort of)
