When an object is thrown with spin, its rotational motion is governed by the principle of angular momentum conservation. Angular momentum is a property of rotating objects and is defined as the product of moment of inertia and angular velocity.
When the object is initially thrown with spin, its angular momentum has a specific direction determined by the initial conditions. According to the law of conservation of angular momentum, the total angular momentum of the system remains constant unless acted upon by an external torque.
As the object rotates in the air, there are two key factors that contribute to its spin being maintained in the same direction:
Torque: When the object is in motion, various forces act upon it, such as air resistance or other external influences. However, these forces generally apply torques to the object in a manner that tends to preserve the initial spin direction. This means that the sum of the torques acting on the object is not sufficient to significantly change the direction of its spin.
Gyroscopic stability: Objects with spin possess gyroscopic stability. This means that the rotating object tends to resist changes to its axis of rotation. The conservation of angular momentum and the object's moment of inertia contribute to this stability. Any attempt to change the spin direction of the object would require the application of an external torque capable of overcoming the object's angular momentum and its resistance to change in rotation.
As a result of these factors, the initial spin of the object is typically maintained rather than randomly changing. However, it's important to note that external influences, such as certain forces or impacts, can affect the object's rotation and potentially alter its spin direction over time.