Answer
The descending mass that should be used is m=2.72 kg
Work Step by Step
The potential energy of the descending mass is converted to heat inside the water (usually use Potential energy if there is a height).
h= (30)(1.25m) As it descends 30 times
m= ?
$\Delta$P = 1000 J
g= 9.8 $m/s^{2}$
Let $\Delta$$P_{grav}$ = $\Delta$$E_{interal energy}$
$\Delta$P=mgh
Rearange the equation to make m your subject of the equation
m=$\frac{\Delta U}{g.h}$
=$\frac{1000J}{(9.8 m/s^{2})(30)(1.25m))}$
=2.72kg
