El arco iris es un fenómeno que se produce principalmente por: I. refracción de la luz
II. reflexión total interna de la luz
III. Interferencia luminosa
a) sólo I
b) sólo II
c) sólo III
d) sólo I y II

In a heat engine if 1000 j of heat enters the system the piston does 500 j of work, what is the final internal energy of the system if the initial energy was 2000 j ?

Does work output exceed work input when a machine is used? a) yes, it does, as machines create energy. b) it depends on the type of machine used. c) no, it doesn’t, as machines are inefficient. d) no, it doesn’t, as machines cannot create energy.

When conducting an investigation to determine which type of fertilizer produces the most flowers on a plant, which variable would be graphed on the x-axis once you collected the data? a. type of fertilizer b. amount of flowers c. amount of water d. number of days that the plants grew