M-CM 2: Forces in circular motion of a particle

PIRA: Unknown

Equipment: large pendulum suspended from ceiling (same as used in M-EngMom1) located in Room 4.

Procedure: Previous discussions and demonstrations should have acquainted the students with the resolution of forces on objects on inclined planes and objects suspended by cords. If this pendulum is pulled to one side and then started by an impulse of just the right amount at right angles to its displacement from the equilibrium position, it will move in a circle in a horizontal plane. Since the motion lies in the horizontal plane, the resultant of all forces on the pendulum must lie in this plane. Hence, the demonstrator can resolve all forces in the horizontal direction to get the value of the resultant (as opposed to resolving perpendicular to the cord as in the swinging pendulum where the motion is always perpendicular to the cord).

This demonstration is chiefly of value because many textbooks treat the example at some length. It is more of a display than a demonstration.