When an arrow is fired, it experiences two main forces: drag and gravity. Drag is the force that opposes the motion of the arrow, and it is caused by the friction between the air and the arrow. Gravity is the force that pulls the arrow down to the ground.

The mass of an arrow affects both of these forces. A heavier arrow will experience more drag, but it will also be less affected by gravity. This means that a heavier arrow will have a lower velocity, but it will also have a greater penetration power.

In addition, the mass of an arrow also affects its momentum. Momentum is the product of an object's mass and velocity. A heavier arrow will have a greater momentum, and this will also increase its penetration power.

Therefore, the mass of an arrow does have an effect on its penetration power. A heavier arrow will have a lower velocity, but it will also have a greater penetration power.