What causes seafloor spreading, subduction, and the movement of
tectonic plates?

Subduction happens where tectonic plates crash into each other instead of spreading apart. At subduction zones, the edge of the denser plate subducts, or slides, beneath the less-dense one. The denser lithospheric material then melts back into the Earth's mantle. Seafloor spreading creates new crust.

Explanation:

hope it helps i do not know if that is the kind of answer you wanted or not but i tried

not too sure thinking it will always be directed towards the centre of the earth. could be wrong not sure

force is mass*acceleration.

we have a very small mass: 11.4*0.001 kg

if we want 0.035n of force, we need an acceleration:

0.035 = 11.4*0.001*a

a = 0.035/(11.4*0.001) m/s^2