Sand is being dropped from a stationary dropper at a rate of \( 0.5 \, \text{kg s}^{-1} \) on a conveyor belt moving with a velocity of \( 5 \, \text{m s}^{-1} \). The power needed to keep the belt moving with the same velocity will be:
\( 1.25 \, \text{W} \)
\( 2.5 \, \text{W} \)
\( 6.25 \, \text{W} \)
\( 12.5 \, \text{W} \)