Two small objects each with a net charge of +q exert a force of magnitude f on each other: we replace one of the objects with another whose net charge is +4q: the original magnitude of the force on the +q charge was f; what is the magnitude of the force on the +q charge now?

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.