In order to figure out what is in a sealed box, you perform some tests. The box seems heavy for its size and is harder to remove from a steel table than when placed on a concrete floor. What kind of object could be inside the box?"

Why this works

This riddle plays on the properties of magnets and their interactions with different materials. The clues about the box feeling heavy and being difficult to remove from a steel table suggest that the object inside has a strong magnetic attraction to steel. On a concrete floor, however, there’s no magnetic attraction, making it easier to move the box. Thus, the answer is a magnet, as its weight and behavior with the steel table perfectly fit the scenario described in the riddle!