Originally Posted by

**topsquark** I need to add two comments to ticbol's answer to part b.

The first is a technical comment:

This is the equation for the vertical component of the __velocity__. With a coordinate system defined such that vertical upward is the positive direction, this answer will indeed be negative. But the question is asking for the speed, which is the magnitude, or size, of the velocity. This number can never be negative.

The second thing is that the ball has a horizontal component to its velocity as it hits the floor, since it had one when it left the table. (There is nothing in the horizontal direction to impede the motion, so there will be no acceleration in the horizontal direction.)

So we have a horizontal component of velocity of vh = 5 ft/s and a vertical component of vv = -16 ft/s. To find the speed (magnitude of the velocity) we need to add these two vectorally. You can draw the picture and, as usual, the components form a right triangle with the velocity vector. So the speed will be:

v = sqrt{vh^2 + vv^2} = sqrt{(5)^2 + (-16)^2} = 16.763 ft/s

-Dan