You are on the flight deck of orbiting space shuttle Discovery and someone hands you two wooden balls, outwardly identical. One , however, has a lead core but the other does not. Describe several ways of telling them apart.

True weightlessness can be achieved only in deep space. Since the space shuttle is orbiting, thus the space shuttle and astronaut (you) in the space shuttle are not even approximately in an inertial frame. Thus the free fall acceleration appears to be zero in that frame. So, the two balls which have mass but they are weight less in the space shuttle. When the space shuttle moves along a curved path, due to the property of inertia the ball which has greater mass (assume the wooden ball which has lead core) will less displace and the ball which has less mass (wooden ball) will more displace. Therefore you can separate the two wooden balls on the basis of inertia.