When you walk across the carpet and touch a metal doorknob, you create a spark. This occurs because .

A. there is an electric field around the carpet
B. you have produced enough static electricity to produce a spark
C. the doorknob has an electric current
D. you have produced an electric current

At a sand and gravel plant, sand is falling off a conveyor and onto a conical pile at a rate of 16 cubic feet per minute. the diameter of the base of the cone is approximately three times the altitude. at what rate is the height of the pile changing when the pile is 12 feet high? (hint: the formula for the volume of a cone is v = 1 3 πr2h.)

Question and answers are in the attached picture. you so much in advance.

Can you simplify 4/7? 24 points will be awarded!