Which of the following is false? question a., light energy from the sun warms the surface of the earth’s continents and the ocean. choice b., approximately 50% of the sun’s light energy does not reach the surface of the earth. choice c., the earth radiates heat energy back to the atmosphere. choice d., much of the heat that is lost from the earth’s surfaces is re-radiated back into the atmosphere by greenhouse gases. choice e., the greenhouse gases in the atmosphere have all come from human activity

Aparticle's position is given by x = 3.00 - 9.00t + 3t2, in which x is in meters and t is in seconds. (a) what is its velocity at t = 1 s? (b) is it moving in the positive or negative direction of x just then? (c) what is its speed just then? (d) is the speed increasing or decreasing just then? (try answering the next two questions without further calculation.) (e) is there ever an instant when the velocity is zero? if so, give the time t; if not, answer "0". (f) is there a time after t = 3 s when the particle is moving in the negative direction of x? if so, give the time t; if not, answer "0".