6. (a) a small styrofoam bead with a mass of 18.2 g and a charge of −0.682 μc is suspended in equilibrium above the center of a large, horizontal sheet of plastic that has a uniform charge density on its surface. find the charge per unit area on the plastic sheet (in μc/m2). (b) what if? what are the magnitude and direction of the acceleration of the piece of styrofoam if its charge is doubled? (enter the magnitude in m/s2.)

More solar radiation is absorbed by earth’s surface than by

Consider the growth of a 20-nm-diameter silicon nanowire onto a silicon wafer. the temperature of the wafer surface is maintained at 2400 k. assume the thermal conductivity of the silicon nanowire is 20 wm-1k-1 and all its surfaces including the tip are subjected to convection heat transfer with the coefficient h = 1×105 wm-2k-1 and t∞ = 8000 k. when the nanowire grows to l = 300 nm, what is the temperature of the nanowire tip (t (x =

Cells in the nervous system have a potential difference of 70 mv across the cell membrane separating the interior of the cell from the extracellular fluid. this potential difference is maintained by ion pumps that move charged ions across the membrane. is this an emf? select the correct answer and explanation. 1)no. the ion pumps cannot separate charges; thus, they cannot create a potential difference. 2)yes. the ion pumps cannot separate charges, but they still can create a potential difference. 3)yes. the ion pumps can actively separate charge; thus, they can create a potential difference. 4)no. the ion pumps can separate charges, but they cannot create a potential difference.