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How to Figure out Pulleys' Speeds

Determining the speed of a pulley, or any other object whose motion is governed by rotational mechanics, is an elementary trigonometry exercise. In determining the speed of a pulley, one uses a simple equation that relates rotational speed with classical Newtonian mechanics. It is important to note the distinction between rotational speed and angular velocity. Rotational speed is a measure of how many complete revolutions are achieved per minute. Angular velocity is a measure of the distance traversed by a point on the edge of a circular object in a given unit of time.

Instructions

- 1
  Multiply the number of rotations per second by 360 degrees. For example, if a pulley rotates two times per second, 2 * 360 = 720 degrees per second.
- 2
  Multiply the resulting value by π / 180. This converts the measurement from degrees to radians. Though this step is not absolutely required, it is highly recommended as any further usage of the derived speed requires radian units. Continuing from above, 720 * π / 180 = 720π / 180 = 4π per second.
- 3
  Multiply the resulting angular speed by 60 seconds. This changes the angular speed to rotational speed in terms of revolutions per minute. Thus, (4π radians / second) * ( 60 seconds / 1 minute ) = 240π radians of revolution per minute.

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