Sally and Bob are mopping the same size floor with the same force of 28 N on the mop. Distance covered was 31 meters. Sally finishes in 15 minutes and Bob does it in 18 minutes. Calculate the work done by Sally and Bob in Joules.

The two stars in a certain binary star system move in circular orbits. the first star, alpha, has an orbital speed of 36 km/s. the second star, beta, has an orbital speed of 12 km/s. the orbital period is 137 d. a) what is the mass of the star alpha? b) what is the mass of the star beta?

Why do astronauts in the space shuttle weigh less?

Select for each of the following statements whether it is correct or incorrect. (a) in an isothermal expansion of an ideal gas. (b) the temperature remains constant. (b) the pressure remains constant. (c) there is work done by the gas. (d) there is heat added to the gas. (e) the change in internal energy equals zero.