The motion (or lack of motion) of the suspension point of an object is observed when the object is struck a blow.
What it shows
The center of percussion (COP) is the place on a bat or racket where it may be struck without causing reaction at the point of support. When a ball is hit at this spot, the contact feels good and the ball seems to spring away with its greatest speed and therefore this is often referred to as the sweet spot. At points other than this spot, the bat or racket may vibrate or even sting your hands. This experiment shows the effect by demonstrating what...
An object rolling down a hill acquires both translational and rotational kinetic energy. One must take the rotational kinetic energy into account when calculating the object's velocity at the bottom of the hill
A very large cable spool (or smaller version) is made to roll in either direction or slide, depending on the angle of pull; action of a torque.
What it shows:
Depending upon the angle of applied force, a yo-yo can be made to roll forwards, backwards or simply slide without rotating.
How it works:
The effect of force angle is illustrated in figure 1; (a) and (b) are the extreme cases. For (a), pulling the string vertically creates a torque r1F rotating the yo-yo counter-clockwise. Pulling the string horizontally as in (b) creates a...
A simple and convincing demonstration of the intermediate axis theorem. Consider an object (a tennis racquet in this case) with three unequal principle moments of inertia. If the racquet is set into rotation about either the axis of greatest moment or least moment and is thereafter subject to no external torques, the resulting motion is stable. However, rotation about the axis of intermediate principle moment of inertia is unstable — the smallest perturbation grows and the rotation axis does not remain close to the initial axis of rotation.
One can show that the period of oscillation of an object doesn't change for different suspension points, as long as they're the same distance from the COM. This is consistent with what the parallel-axis theorem tells us about the moment of inertia of the object.
How it works:
The parallel-axis theorm states that if Icm is the moment-of-inertia of an object about an axis through its center-of-mass, then I, the moment of inertia about any axis parallel to that first one is given by I = Icm +...
Allow a board to rotate under the force of gravity and the free end will accelerate at a rate greater than g. Relation between angular acceleration and linear acceleration seems to give free-fall paradox.
How it works:
If a board, held in a vertical position with one end resting on the...