Four point charges, each of magnitude 12.6 µc, are placed at the corners of a square 92.7 cm on a side. if three of the charges are positive and one is negative, find the magnitude of the force experienced by the negative charge. the value of coulomb’s constant is 8.98755 × 109 n · m2 /c 2 . answer in units of n

At 20∘c, the hole in an aluminum ring is 2.800 cm in diameter. you need to slip this ring over a steel shaft that has a room-temperature diameter of 2.804 cm . 1. to what common temperature should the ring and the shaft be heated so that the ring will just fit onto the shaft? coefficients of linear thermal expansion of steel and aluminum are 12×10−6 k−1 and23×10−6 k−1 respectively.