Atennis player is hitting a 58 gram tennis ball back across the net. when the racquet and the ball first make contact, the ball is moving at 30 m/s 15⁰ below the positive x-axis. when the ball leaves the racquet, it is moving at 40 m/s 15⁰ above the negative x-axis. if the ball is in contact with the racquet for 0.08 s, what is the average net force acting on the tennis ball while it is in contact with the racquet? air resistance and the force of gravity are negligible when compared to the force by the tennis racquet.

Which of the statements about waves is true? a. in longitudinal waves, particles move perpendicular to the direction the wave is traveling. b. both transverse and longitudinal waves can travel through water c. electromagnetic waves are a type of longitudinal waves. d. in a transverse wave, particles move parallel to the direction the wave is traveling.

An internally reversible refrigerator has a modified coefficient of performance accounting for realistic heat transfer processes of where qin is the refrigerator cooling rate, qout is the heat rejection rate, and is the power input. show that copm can be expressed in terms of the reservoir temperatures tc and th, the cold and hot thermal resistances rt, c and rt, h, and qin, as where rtot rt, c rt, h. also, show that the power input may be expressed as 1.39 a household refrigerator operates with cold- and hot-temperature reservoirs of tc 5 c and th 25 c, respectively. when new, the cold and hot side resistances are rc, n 0.05 k/w and rh, n 0.04 k/w, respectively. over time, dust accumulates on the refrigerator’s condenser coil, which is located behind the refrigerator, increasing the hot side resistance to rh, d 0.1 k/w. it is desired to have a refrigerator cooling rate of qin 750 w. using the results of problem 1.38, determine the modified coefficient of performance and the required power input w under (a) clean and (b) dusty coil conditions. internally reversible refrigerator qout qin w high-temperature reservoir low-temperature reservoir th th, i tc, i tc high-temperature side resistance low-temperature side resistance w qin th tc qinrtot tc qinrtot copm tc qinrtot th tc

The flame produced by the burner of a gas (propane) grill is a pale blue color when enough air mixes with the propane (c3h8) to burn it completely. for every gram of propane that flows through the burner, what volume of air is needed to burn it completely? assume that the temperature of the burner is 195.0°c, the pressure is 1.05 atm, and the mole fraction of o2 in air is 0.210.