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
Official Solution incorrect? by Kenny M)
I said "correct" because Charlie hit the main point - the system included both a conservative force (gravity) and non-conservative forces (the most important being friction). So, had the system involved the conservative force gravity only, the skier would have come out the bottom barreling at nearly 100 mph. So yes, the professor gave a lousy example that included both types of forces and thereby proved nothing.
As opposed to "conservative forces" (useful in solving e.g., mechanical and electrostatic problems with a lot of mathematical finesse) the more common "conservation of ___" (e.g. energy, force, mass, energy, momentum, charge) is used also to solve many problems but in a more housekeeping-like manner (it must have gone somewhere....) . In the ski example, a lot of potential energy went into pushing and melting snow, and redirecting wind.
(Oh, I just looked at the "official" answer - yes - it's wrong)
Edited on February 26, 2023, 1:40 pm
re: Official Solution incorrect?
