If you drop a rock from a height of 13 m, it accelerates at 9.8 m/s2 and strikes the ground 1.62882 s later. If you drop the same rock from half that height, what will be its acceleration?

You had me worried there for a second.  I thought you were going to ask how much the time changes, or how much the speed changes as it hits the ground, and I was gonna skip this question and go to bed.

But the acceleration won't change.  That's always 9.8 m/s².  That's the acceleration of gravity on Earth. It doesn't depend on what you drop, or what its mass is, or how heavy it is, or what color it is, or how high you drop it from. The only way you can change it is to drop the rock through air or water, or on a different planet.

the answer would be   dignified - apex

5 w for 1hr = 5x60x60 joules=300x60=3000x6=18,000j as total energy conversion. efficiency of bulb needed for radiant to thermal within 18000