Two red blood cells each have a mass of 7.50×10−14 kg and carry a negative charge spread uniformly over their surfaces. the repulsion arising from the excess charge prevents the cells from clumping together. once cell carries −1.80 pc of charge and the other −3.30 pc , and each cell can be modeled as a sphere 6.80 μm in diameter. what minimum relative speed would the red blood cells need when very far away from each other to get close enough to just touch? ignore viscous drag from the surrounding liquid.