what efficiency is the machine using in obtaining this result? % If your actual efficiency is 0.19, how many kcal did you really burn? kcal

Suppose you spend 30.0 minutes on a stair-climbing machine, climbing at a rate of 65 steps per minute, with each step 8.00 inches high. If you weigh 150 lb and the machine reports that 750 kcal have been burned at the end of the workout, what efficiency is the machine using in obtaining this result? %If your actual efficiency is 0.19, how many kcal did you really burn? kcal

An ice cube at 0.0°C is slowly melting. What is the change in the ice cube’s entropy for each 5.80 g of ice that melts? Latent heat of fusion of ice is 333.7 J/g.

A power plant operates at a 25.0% efficiency during the summer when the seawater used for cooling is at 20.0°C. The plant uses 360°C steam to drive turbines. If the plant's efficiency changes in the same proportion as the ideal efficiency, what would be the plant's efficiency in the winter, when the seawater is at 10.1°C? ______ %

9) A heat pump is used to move heat from 10°C air outside, to a 22 °C air inside. The practical coefficient of performance of this pump is 4.1, and it uses 12000 J of electric energy. a) Find the energy this system adds to the house. b) Find the theoretical (maximum) coefficient of performance for this system. 5

The coefficient of performance of a refrigerator is 5. If the temperature of the room is 301K, what is the lowest possible temperature that can obtained insides the refrigerator ? a) - 44.2°C b) 22.2°C c) - 22.2°C

A certain coal-fired power plant has a rated power capacity of P = 850 MW. The output of this plant is W = 0.21QH, where QH is the energy input as heat from the hot reservoir. a) Which would increase the efficiency more, doubling QH or reducing QC by half?  b) Calculate the maximum thermal efficiency of the power plant.  c) Calculate the absolute value of the exhausted heat (QC) each second in MJ for the power plant.  d) If the power plant operates for a full day at its rated capacity, how much energy QH in MJ is needed?  e) If, on average, one ton of coal contains Q = 25 GJ of energy, how many tons nH of coal would the plant need to operate for a day at its rated capacity?  f) How many tons nC of this coal is exhausted as wasted heat to QC in a single day?