Aheat engine is to operate by rejecting wasted energy as heat to a river that has a mean temperature of 12° c. what must the minimum temperature of its energy source be if it is to produce work with an efficiency of 0.75 (i. e., 75%)?

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.