Currently, the concentration of carbon dioxide in Earth's atmosphere is about 400 parts per million. During the Cretaceous Period, about 110 million years ago, the concentration of carbon dioxide in Earth's atmosphere was about 2,000 parts per million. Based on your knowledge of the greenhouse effect, how do you think the average temperature on Earth 110 million years ago compared to the temperature in modern times?

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".