Being one to observe all safety warning signs, JD lets the world know what you're NOT supposed to do while observing Nevada Falls at close range.   The fine print has a simple, direct message.  It says, "If you fall in, you will die."  And they are right!  Nevada Falls is some 250ft tall and carries the entire Merced river over its wall.

Pretty good imitation of the falling man depicted on the sign, don't you think?  "Hey John, let's go down the trail a piece and run a physics experiment.  You pose just like that on the slippery rocks and I'll record the action.  Deal?  You know S=1/2at**2+vt+s0.  We'll test to see if actions and reaction are equal, the height was measured properly, stopping 180lbs at the bottom ain't all that hard, etc.  What do you say?"