Author Question: In a problem using energy considerations to solve for the speed of a ball thrown from the top of a ... (Read 45 times)

dmcintosh · **on:** Jul 28, 2018

In a problem using energy considerations to solve for the speed of a ball thrown from the top of a building when it strikes the ground below, where should the potential energy have its zero value?
a. It should be at the level from where the ball is thrown.
b. It should be at the ground level where the ball hits.
c. It should be slightly below ground level so the potential energy is always positive.
d. It doesn't matter since only differences in potential energy matter in solutions.

Question 2

An electrical generating plant operates at a boiler temperature of 220C and exhausts the unused heat into a nearby river at 19C. If the generating plant has a power output of 800 megawatts (MW) and if the actual efficiency is 3/5 the theoretical efficiency, how much heat per second must be delivered to the boiler? (0C = 273 K)
a. 5200 MW
c. 3270 MW
b. 1810 MW
d. 2620 MW