Tracy and eric are timing how fast marbles roll down an inclined plane. they plan to do this 5 times, and then take the average time for their results. what would be best way to improve the accuracy of their data?

a. include marbles of three different colors
b. include the average of 20 trials down the inclined plane
c. use marbles of ten densities
d. use toy cars instead of marbles

Two kilograms of air within a piston–cylinder assembly executes a carnot power cycle with maximum and minimum temperatures of 800 k and 300 k, respectively. the heat transfer to the air during the isothermal expansion is 60 kj. at the end of the isothermal expansion the volume is 0.4 m3. assume the ideal gas model for the air. determine the thermal efficiency, the volume at the beginning of the isothermal expansion, in m3, and the work during the adiabatic expansion, in kj.