You can't. Velocity and acceleration measure two different things, so their units are incompatible. It's like asking, "How many meters does this book weigh?"
Maybe you mean "find" acceleration using given velocities, or a velocity function?
Tectonic plates and convection cells move tectonic plates
During the falling down, two forces are present: gravitational force and air resistance.
So, the net force = mg - f = 12*9.8 - 27 = 90.6 N, the positive sign indicates the direction is pointing towards the center of the earth, which is the same as gravitational force
Chiefly in science fiction) an invisible barrier of exerted strength or impetus.