Aroller coaster car is elevated to a height of 30 m and released from rest to roll along a track. at a certain time t it is at a height of 2 m and has lost 25.000 j of energy to friction. the car has a mass of 800 kg. answer the following questions. (a) how fast is the car going at time t? (b) how fast would the car be going at time t if the track were frictionless?

Scientist have use computer models to create a series of maps that show how susceptible coastal cities in island countries are to the sea rising at different levels.the map shows that a 1 meter rise would swap cities all along the us eastern seaboard. a 6-meter sea level rise with sub merge a large part of florida. thermal expansion has already raise the oceans 10 to 20 centimeters the most likely cause,directly and indirectly, for such a rise in sea level is