A hoop has mass and radius of 4 kg and 0.37 m, respectively. The hoop start from rest and has a constant angular acceleration with respect to a rotational axis that is perpendicular to the plane of the hoop at its center. The hoop turns through an angle of 16 rad in 6.3 s. Find the net external torque that acts on the hoop.

Four point charges each having charge q are located at the corners of a square having sides of length a. find symbolic expressions for the following. (a) the total electric potential at the center of the square due to the four charges (use any variable or symbol stated above along with the following as necessary: ke.) vtotal= (b) the work required to bring a fifth charge p from infinity to the center of the square (use any variable or symbol stated above along with the following as necessary: w=

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