A ball is thrown into the air with 100 J of kinetic energy, which is transformed to gravitational potential energy
at the top of its trajectory. If it returns to its original level less than 100 J of kinetic energy, the ball
encountered
a. air resistance.
b. gravitational acceleration.
c. a faster descent time.
d. a decrease of its mass.

8.29 two streams containing pyridine and acetic acid at 25°c are mixed and fed into a heat exchanger. due to the heat-of-mixing effect, it is desired to reduce the temperature after mixing to 25°c using a stream of chilled ethylene glycol as indicated in the diagram. calculate the mass flow rate of ethylene glycol needed. the heat capacity of ethylene glycol at these conditions is approximately 2.8 kj/(kg k), and the enthalpy change of mixing (δmixh) is given below.