A particle is to move in an xy plane, clockwise around the origin as seen from the positive side of the z axis. In unit-vector notation, what torque acts on the particle if the magnitude of its angular momentum about the origin is (a) 4.0 kg ⋅ m2/s, (b) 4.0t2 kg ⋅ m2/s, (c) 4.0 √ t kg ⋅ m 2 / s and (d) 4.0/t2 kg ⋅ m2/s?

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?

Two point charges are separated by a certain distance. how does the strength of the electric field produced by the first charge

2) a cubical block of stone is lowered at a steady rate into the ocean by a crane, always keeping the top and bottom faces horizontal. which one of the following graphs best describes the buoyant force b on this block as a function of time t if the block just enters the water at time t = 0 s?