gravitational
effects of nearly-elastic collisions
along with
Maxwell's wheel is the classic way of showing the interplay between potential energy and kinetic energy, along with the effects of nearly-elastic collisions.
Maxwell's wheel consists of an axle-mounted flywheel suspended by nylon cords at both ends. Wind it up to the top of the frame and let it go! As it drops, gravitational potential energy changes to kinetic energy of the wheel's descent and rotation. When it has unwound to the bottom, the sharp jerk on reaching the end of the nylon cords reverses its linear momentum (while maintaining its angular momentum). This "collision" at the bottom is nearly elastic - some of the kinetic energy is lost. The ratio of energy kept to starting energy tells you how "elastic" the collision was through its coefficient of restitution.
Just be careful to keep the frame level and the cords even when you suspend the flywheel.
Maxwell’s pendulum consists of a wheel hanging by two wires which are wound in the same direction on an axis passing through its centre of gravity. Once released, the wheel comes down under the action of its weight , but it is forced to rotate in order to unwind the two wires. It slowly comes down (low kinetic translation energy) but it rotates rapidly (high kinetic rotary energy).
At the end of the fall the total kinetic energy, not considering the losses, has to be equal to the gravitational energy supplied at the beginning. After the wires have been unwound, the wheel goes on rotating rewinding the wires on its axis and coming back up. If there were no friction, it would go up to the initial level of its fall. The falling and rising motion is repeated more than once with
a period that depends on the initial height difference h, on the acceleration due to gravity g and on the relationship between the radius of the wheel and the radius of its pivot. Through the position sensor it possible to evaluate at which speed the wheel gets
to at the end run point and to perform accurate measurements.