Select each correct answer. More than one answer may be correct. Which of the following forces between two objects can be repulsive?
gravitational force
magnetic force
electrostatic force

Glass has a hardness that is in the middle of the hardness scale. what is the hardness of glass?

What causes the development of most clouds and precipitation in the atmosphere?

Two kilograms of air within a piston–cylinder assembly executes a carnot power cycle with maximum and minimum temperatures of 800 k and 300 k, respectively. the heat transfer to the air during the isothermal expansion is 60 kj. at the end of the isothermal expansion the volume is 0.4 m3. assume the ideal gas model for the air. determine the thermal efficiency, the volume at the beginning of the isothermal expansion, in m3, and the work during the adiabatic expansion, in kj.