Final answer:
When an object experiences angular deceleration, it means that the torque being applied is negative, which results in the object slowing down its rotational motion.
Step-by-step explanation:
When something has an angular deceleration, the torque applied to the system is negative. This means that the force causing rotation is acting in the opposite direction to the object's rotation, thereby causing it to slow down. To understand this, one can consider torque as the rotational equivalent of force in linear motion. Just as a net force causes an acceleration, a net torque causes an angular acceleration. If you push far from the pivot point on an object, such as a door, the greater the angular acceleration you create, which essentially relates force, mass, and radius to angular acceleration.
In the context of rotational dynamics, torque is calculated as the product of the force applied and the distance from the axis of rotation, known as the lever arm. If this torque is causing the object to decelerate, then the angular acceleration it causes is negative. For example, when a girl spins a wheel and then hits the brake, a large negative angular acceleration is generated, and the torque in this case would also be negative, causing the angular velocity of the wheel to rapidly decrease.