What comes before Action-reaction?

What happens in a global convection cell

Calculate the amount of heat produced when 18000 coulombs of charge is transferred in one hour through a potential difference of 50v

The crank oa rotates in the vertical plane with a constant clockwise angular velocity ω0 of 5.6 rad/s. for the position where oa is horizontal, calculate the force under the light roller b of the 10.6-kg slender bar ab.