Why does the momentum before a collision equal the momentum after a collision? a) because velocity is conserved b) because force times mass equals acceleration c) because momentum is conserved

Aboy with a mass 25 kg climbs into a small tree. he sits on a branch that is 2.o m above to the ground. what is his gravitational potential energy above the ground?

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.

If you visited mount shasta city (elevation 900 m [3000 ft.]) and found the outside air temperature to be 27°c (81°f), what would be the air temperature at the summit of mount shasta (elevation 4200 m [14,000 ft.]) at that moment-assuming that the temperature conditions with altitude change at an average, or normal, lapse rate?