Problema de mecanica.

What is the force that opposes motion and works against the downward pull? a) friction b) gravity c) weight d) acceleration

2) a cubical block of stone is lowered at a steady rate into the ocean by a crane, always keeping the top and bottom faces horizontal. which one of the following graphs best describes the buoyant force b on this block as a function of time t if the block just enters the water at time t = 0 s?

Look at the electroscope, describe how you can cause the two leaves at the bottom to repel each other and stay that way