Physics
posted by Max .
Two plates, each of area 3.40*104 m2, are used to construct a parallelplate capacitor with capacitance 1.20 pF.
(a) Find the necessary separation distance.
d = ?m
(b) If the positive plate is to hold a charge of 4.70* 1012 C, find the charge density.
σ = ?C/m2
(c) Find the electric field between the plates.
E = ?N/C
(d) What voltage battery should be attached to the plate to obtain the preceding results?
V = ?V

For (a), find the formula for C in terms of epsilon, Area and plate separation. For (b), divide the charge by the area. For (c), use Gauss law and the charge density for the E field . For (d), use V = E*d
Show your work if you need further assistance. 
In the figure here, a red car and a green car move toward each other in adjacent lanes and parallel to an x axis. At time t = 0, the red car is at xr = 0 and the green car is at xg = 223 m. If the red car has a constant velocity of 22.0 km/h, the cars pass each other at x = 44.7 m. On the other hand, if the red car has a constant velocity of 44.0 km/h, they pass each other at x = 76.6 m. What are (a) the initial velocity (in km/h) and (b) the (constant) acceleration (in m/s2) of the green car?