A student of 50 kg has been sitting at same spot for over 2 hours and studying for his final exam. How much work in Joules (J) has he
accomplished?

it doesn't. it was imagined up in the middle ages.

the components of a vector are the parts of the vectors that are to each other.

b perpendicular

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.