To increase a baseball's acceleration, you must increase the applied force, according to Newton's Second Law of Motion (F = ma); a greater force applied to the ball will cause a greater acceleration.
To increase the acceleration of a baseball when you throw it, you must increase the force applied to the ball while keeping its mass constant. According to Newton's Second Law of Motion, acceleration (a) is directly proportional to the net external force (F) applied on an object and inversely proportional to its mass (m), as illustrated by the equation F = ma.
Therefore, if you want to achieve a higher acceleration, applying a greater force is the key. However, keep in mind that increasing the mass of the object would have the opposite effect on its acceleration due to the inverse relationship between mass and acceleration in this law.
For instance, if a pitcher wants the baseball to reach the catcher faster, he would need to throw the ball with more force. This increase in force, if no other changes are made, would result in a higher acceleration of the baseball from the point it leaves the pitcher's hand until it reaches the catcher's mitt.
So, the essential factor to increase the acceleration of a baseball during a throw is the force exerted on it.