Picture showing four cards in a row with labels 'first animal appears on land', 'first life form appears in the sea', 'first rocks formed on earth', and 'first flowering plants appear on land'.

a student arranged the four cards sequentially in a row on the basis of the periods when the events occurred. the card showing the earliest event was placed on the extreme left. which of these cards was placed first in the row?

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".