14. On a distant asteroid, a large catapult is used to throw chunks of stone into space. Could such a device be used as a propulsion sys-
tem to move the asteroid closer to the earth? Explain.

Hydroelectricity provides about 7 percent of the electricity generated in the united states. (a) explain how a hydroelectric power plant converts energy stored in water into electricity. (b) identify two factors that determine the amount of electricity that can be generated by an individual hydroelectricity power plant. (c) describe the two main types of land-based hydroelectric power plants. (d) describe two economic advantages and two environmental disadvantages of hydroelectricity.