A student lifts their 5 kg backpack 2 meters off the floor. How much work does the student do on the backpack? 5/2= 2.5 J
5 x 2 = 10 W
5/2 = 2.5 W
5 x 2 = 10 J

An ice-making machine inside a refrigerator operates in a carnot cycle. it takes heat from liquid water at 0.0 degrees celsius and rejects heat to a room at a temperature of 19.2 degrees celsius. suppose that liquid water with a mass of 76.3kg at 0.0 degrees celsius is converted to ice at the same temperature. take the heat of fusion for water to be l_f = 3.34*10^5 j/kg.how much energy e must be supplied to the device? express your answer in joules.