Based on the second law of thermodynamics why must a machine always be less than 100% efficient?
a. heat never moves from cold to hot.
b. heat is never converted completely into mechanical energy.
c. heat never flows from hot to cold.
d. entropy never increases.

Which of the following is not a part of a wave? question 2 options: a: frequency b: refraction c: wavelength d: amplitude (whoever answers correctly first gets brainiest! ) ~kayla

3. on your graph, the data points between the black squares are data for elements with atomic numbers 3 through 9. locate these elements on your periodic table. what term or description would you use to identify these elements with respect to the periodic table?

Balloon a has charge q, and identical mass balloon b has charge 10q. you hang them from threads near each other. choose all of the statements with which you agree. check all that apply. a. a and b exert the same magnitude forces on each other. b. the force that a exerts on b is 10 times the force that b exerts on a. c. the angle between the thread supporting a and the vertical is < the angle between the thread supporting b and the vertical. d. the force that a exerts on b is 1/10 the force that b exerts on a.