The magnitude J of the current density in a certain lab wire with a circular cross section of radius R ! 2.00 mm is given by J ! (3.00 $ 108)r2, with J in amperes per square meter and radial distance r in meters. What is the current through the outer section bounded by r ! 0.900R and r ! R

Review multiple-concept example 7 in this chapter as an aid in solving this problem. in a fast-pitch softball game the pitcher is impressive to watch, as she delivers a pitch by rapidly whirling her arm around so that the ball in her hand moves in a circle. in one instance, the radius of the circle is 0.626 m. at one point on this circle, the ball has an angular acceleration of 66.1 rad/s2 and an angular speed of 12.6 rad/s. (a) find the magnitude of the total acceleration (centripetal plus tangential) of the ball. (b) determine the angle of the total acceleration relative to the radial direction.