PE = mgh KE = 1/2(mv2)
ME = PE + KE
4. If the ball falls from the shelf when it is placed back there, h = 2m What is its speed the
instant before it hits the ground? Set PE = KE and solve for v.

Neil armstrong, the first human being to step on the moon, left a foot print that is essentially unchanged nearly 50 years later. how is it possible for this, and all the other footprints, tracks and markings, left on the lunar surface to remain unchanged for so long?