Ameter stick is balanced at the 50 cm mark. you tie 70 n weight at the 30 cm mark. what weight at the 90 cm mark would create a rotational equilibrium?

Large electric fields in cell membranes cause ions to move through the cell wall. the field strength in a typical membrane is 1.0 x 10 7 n/c. what is the magnitude of the force on a calcium ion with charge +e? what is its acceleration? is it possible for a particle with the same charge as as calcium to have a different acceleration if placed at this location? what would change the acceleration: mass of the particle? diameter of the particle?