A chair of mass 10.5 kg is sitting on the horizontal floor; the floor is not frictionless. You push on the chair with a force F = 38.0 N that is directed at an angle of 43.0 ∘ below the horizontal and the chair slides along the floor.

n=142 N

Explanation:

solution:

pic 1 is attached

There is no vertical acceleration (ay = 0), so net sum of vertical forces is 0. n acts up, weight and the vertical component of F act down, so  

∑F_y =m*a_y  

n-mg-Fsin43°=0

n=142 N

energy can be converted from one form to another, but it cannot be created or destroyed in ordinary chemical or physical means. do not understand what you are asking but hope this