How does the sun maintain its high temperature and energy output?

By not running out of fuel (Hydrogen).

Rest assured ... When the sun runs low on Hydrogen, it'll go through several complex changes, and it'll end up at much much lower temperature, with much much lower energy output.

it about 600 mph from what i calculated

weight of the box is given as

here this is placed on the inclined of angle 42 degree

now this weight will have two components one is along the incline other is perpendicular to it

so here we need to apply a force parallel to incline opposite to its component of weight

so here the component of weight is given as

here we have

so it requires 75 n force to move it upwards