Hint: this problem requires a train of logic. (1) analyze force diagram, (2) use newton’s laws, and (3) solve the equations of motion. a block starts from rest at a height of 3.9 m on a fixed inclined plane. the acceleration of gravity is 9.8 m/s 2 . 3.8 kg µ = 0.12 31◦ what is the speed of the block at the bottom of the ramp? answer in units of m/s.

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".