We can solve this problem by first solving for the total volume of the cube. The formula for volume of cube is given as:
V cube = s^3
Where s is the length of one side which is equivalent to 2 inches. Therefore:
V cube = (2 inches)^3
V cube = 8 cubic inch
Assuming that all the pebble fills the cube without any spaces, then the total weight of the pebbles in the cube would simply be:
Total weight = 0.5 lb per cubic inch * 8 cubic inch
Total weight = 4 lb
Therefore, the total weight of the pebbles in the cube is 4 lbs.