For the cloudy day, does the time of peak longwave radiation coincide with the time of highest surface temperatures, highest solar radiation, or thickest and lowest clouds? Why would this be?

whichever one it is, it's definitely not one that you included on the list you provided.

a displacement distance is size of displ

electrical potential energy =0.072 j

explanation:

electrical potential energy is given by

u= q δv

q= charge=6 c

δv= potential difference and is given by

δv= e d

e= electric field

d= distance=5 mm=0.005 m

δv=2.4 (0.005)=0.012 v

now electric potential energy= u= q δv

u=6 (0.012)

u=0.072 j