Achild is stationary on a swing. the child is given a push by his brother to start him swinging. his brother applies a steady force of 84 n over a distance of 0.25 m. calculate the work done by this force.

The field between two charged parallel plates is kept constant. if the two plates are brought closer together, the potential difference between the two plates either a) decrease b) does not change c) increase?

Two identical stars with mass m orbit around their center of mass. each orbit is circular and has radius r, so that the two stars are always on opposite sides of the circle. (a) find the gravitational force of one star on the other. (b) find the orbital speed of each star and the period of the orbit. (c) how much energy would be required to separate the two stars to infinity?

Apropagating wave in space with electric and magnetic components. these components oscillate at right angles to each other. it may travel in a vacuum.