Suppose a very light ball is thrown at a wall.
The wall may be thought of as an xy-plane.
At the moment the ball hits the wall, does it have 0 velocity in the x, y and z directions?
Is drag on the ball (in each respective direction) small enough to be ignored at the moment the ball hits the wall?
D ~ (Av^2)/4
The Attempt at a Solution
I think the ball momentarily has 0 velocity in the z-axis since the ball is changing direction along this axis.
I think the ball will be slowed in the x and y axes at the moment it hits the wall, but its velocity in these directions will not equal zero at that instant.
Therefore, drag can only be ignored in the z-direction.