An hour glass with sand is placed on a weighing scale with initially all the sand in the  glass held in the upper half. At  $\text{t}=0$ , the sand is released and it exits upper half at  constant rate and speed of the falling sand is zero at the neck of the glass and after it  falls through a constant height, it instantaneously comes to rest on the floor of the hour  glass. The reading of the weighing scale