Listena person on a ledge throws a ball vertically downward, striking the ground below the ledge with 200 joules of kinetic energy. the person then throws an identical ball vertically upward at the same initial speed from the same point. what is the kinetic energy of the second ball when it hits the ground? [neglect friction.]

a. 200 j
b. 400 j
c. less than 200 j
d. more than 400 j

4r-134a enters the condenser of a residential heat pump at 800 kpa and 50°c at a rate of 0.022 kg/s and leaves at 750 kpa subcooled by 3°c. the refrigerant enters the compressor at 200 kpa superheated by 4°c determine (a) the isentropic efficiency of the compressor, (b) the rate of heat supplied to the heated room, and (c) the cop of the heat pump. also, determine (d) the cop and rate of heat supplied to the heated room if this heat pump operated on the ideal vapor-compression cycle between the pressure limits of 200 and 800 kpa. (0.757, 4.37 kw, 5.12, 6.18, 3.91 kw)

What is the efficiency of an engine that does 80 j of work and exhausts 320 j of heat while taking in 400 j of heat ? a. 10% b. 20% c. 80% d. 25%

Which of the following is a measure of the amount of light a star directly emits?               a.  luminosity    b.  intensity    c.  wavelength    d.  brightness