In this dramatic demonstration a massive weight is suspended by a wire from the ceiling of the lecture hall. The demonstrator stands braced against the wall, draws the mass to his nose, and releases it. If conservation of the energy holds, on the return swing the mass will stop just millimeters in front of his nose. But if conservation of energy fails,...!
The lengths of the pendulums in the corresponding lecture halls are as follows:
PAB 1425 | 4.66 m |
KNSY PV 1220B | 4.67 m |
A simple pendulum set swinging will rise to the same height on each side. If a bar interrupts its swing on one side, it will still reach the same height. The position of the bar is variable.
The ball rolling on the track will rise to the same height regardless of how the angle of the raisable side is changed
A ball is rolled down an inclined track which has a vertical 360° loop at the bottom. The rolling ball stays on the track if started from the proper height on the incline. Friction and the rotational energy of rolling must be taken into account. Note that the ball does not roll on its bottom, so it uses even more rotational energy than a rolling sphere.
The maximum horsepower developed by a human being over a few seconds time can be measured by timing a volunteer running up the stairs in the lecture hall. If a person of weight W runs up height h in time t, then h.p. = Wh/t X 1/550 ft-lbs/sec. A person in good shape can develop one to two horsepower. It will be entertaining to the students if the professor tries it too.
Should the person be allowed a running start?