Two red blood cells each have a mass of 6.15 × 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 v 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.