<blockquote><font class="small">In reply to:</font><hr /><p>No force can have an effect at right angles to it's line of action <p><hr /></p></p></blockquote><br /><br />I see the confusion. Basically, that's not what's happening here.<br /><br />Disregarding friction with the pool table and wind resistance, there are two forces involved here. One is gravity. The other is the force imparted by the pool cue. This force is over the moment the ball rolls away, and in accordance with Newton's First Law, the ball remains in motion in a straight line. But then it reaches the edge of the table. Assuming the table has no walls (so it's not a normal pool table at all), the ball rolls off the edge. There is nothing now to counteract gravity, and the ball is accelerated downwards by the constant force of gravity. This happens to be at a ninety-degree angle to the ball's current direction of travel. There is no other force now acting on the ball but gravity. It drops at 9.8 meters per second per second (or meters per second squared). This means that if the ball were falling far enough to take a second to do it, it would be travelling 9.8 meters/second by the end, but if it fell far enough to take two seconds, it would be travelling 19.6 meters/second. That's important to understanding this -- gravity <i>accelerates</i> falling objects.<br /><br />Now, if you drop a second cue ball at exactly the same altitude as the table but off to one side, it'll take just as long to hit the ground as the ball that was pushed off the table. This is because it, too, is being accelerated downward at 9.8 m/s^2. The difference is that the first ball will land directly below where it was dropped (proving that gravity is not somehow acting at right angles to itself) wheras the first ball will land some distance away, since it did not lose any of its initial momentum when it left the table. If you hit a third ball harder than the first, it will land further away than the first ball. But it too will lan <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em> -- The Tenth Doctor, "Blink"</font></p> </div>