Air at 10°c enters a 12-cm-diameter and 5-m-long pipe at a rate of 0.065 kg/s. the inner surface of the pipe has a roughness of 0.22 mm, and the pipe is nearly isothermal at 50°c. determine the rate of heat transfer to air using the nusselt number relation given by (a) eq. 8–66 and (b) eq. 8–71. evaluate air properties at a bulk mean temperature of 20°c. is this a good assumption?

Atennis player used a tennis racket to hit a tennis ball with a mass of 0.25 kg with a force of 5.25 newtons. how does the force the tennis racket exerted on the tennis ball compare with the force the tennis ball exerted on the tennis racket? a. the force of the tennis racket on the tennis ball is equal in magnitude and opposite in direction to the force the tennis ball exerted on the tennis racket. b. the force of the tennis racket on the tennis ball is equal in magnitude and in the same direction as the force the tennis ball exerted on the tennis racket. c. the force of the tennis racket on the tennis ball is less in magnitude and in the same direction as the force the tennis ball exerted on the tennis racket. d. the force of the tennis racket on the tennis ball is greater in magnitude and opposite in direction as the force the tennis ball exerted on the tennis racket.