. A 90-kg man stands in an elevator that is moving up at a constant speed of 5.0 m/s. The force exerted by him on the floor is about: A) 0 N B) 90 N C) 880 N D) 450 N E) 1330 N

the answer is c. the lower legs are levers, and the knees are fulcrums. the ankles hold the loads.

in most common fires, oxygen is needed for an oxidation reaction to takes place. the combination of oxygen with any element as fuel can create fire and combustion will occur especially if wood, light materials and other combustible things are combine with oxygen.