A bug sits on the edge of a rotating disk. Later, the bug begins to move toward the center of the disk. Does the bug exert a torque on the disk?
To determine whether the bug exerts a torque on the disk, we need to consider the factors that contribute to torque. Torque is the rotational equivalent of force, causing an object to rotate around an axis. It depends on two main factors: the magnitude of the force applied and the perpendicular distance between the axis of rotation and the line of action of the force.
In this case, the bug is moving toward the center of the disk. As the bug moves inward, it exerts a force in the outward direction (toward the rim of the disk) due to Newton's Third Law of motion, which states that every action has an equal and opposite reaction.
However, the force exerted by the bug is always directed radially outward, perpendicular to the radius of the disk, and passes through the axis of rotation. Since the line of action of the force passes through the axis of rotation, the perpendicular distance between the axis and the force is zero.
In torque calculations, when the perpendicular distance is zero, the torque is also zero. Therefore, in this scenario, the bug does not exert a torque on the disk as it moves toward the center.