Final answer:
Angular speed, measured in rad/s, describes how quickly a wheel rotates. A bicycle wheel with an angular speed of 4π rad/s rotates twice per second. Angular velocity also indicates the direction of rotation.
Step-by-step explanation:
The angular speed of a wheel is a measure of how quickly it rotates around its axis, typically given in radians per second (rad/s). With an angular speed of 4π rad/s, a bicycle wheel completes 2 revolutions per second because 2π rad corresponds to one full revolution. Hence, the wheel's rotation can be described in terms of the angular velocity, which is a vector quantity encompassing both magnitude (speed) and direction of rotation.