Understanding Gravity and Arrow Velocity: A Simple Explanation

[Iainhol]

I am currently at my in-laws in VT where a hunting debate came up. They say that gravity is slowing down the arrow. I stated that the x and the y act independently, therefore the forward momentum is the same. The only force slowing the arrow down is friction from air, therefore if there was no air the velocity would be the same (Newton's second law). Am I correct?

 

[Doc Al]

As the arrow rises, gravity acts to slow it down; as it falls, gravity acts to speed it up. Just like any other projectile. But you are correct that, ignoring air resistance, the horizontal component of the velocity would remain unchanged.