Astronauts Dustin and Justin and are exploring the depths of outer space far from any planet or star. Just for fun, Dustin, whose mass is 80 kg, decides to give Justin, whose mass is 90 kg, a 60 N push to the right, as shown below. (a) How does this push affect the motion of Dustin and Justin? Be as quantitative as possible.
(b) Now suppose that it was Justin that pushed Dustin to the left with a force of 60 N. How does your answer to (a) change? Explain.
(c) Finally, suppose that Justin and Dustin have the same mass. How does this affect your answer to (a)?

PIC IS IN THE DOC!

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".