Aparticle's position is given by x = 7.00 - 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".

a. The particle has velocity at time ,

so that after it will have velocity .

b. The sign of the velocity is negative, so it's moving in the negative direction.

c. Its speed is 3.00 m/s.

d. The particle's velocity changes according to

which is positive and indicates the velocity/speed of the particle is increasing.

e. Yes. The velocity is increasing at a constant rate. Solving for is trivial; this happens when .

f. No, the velocity is positive for all beyond 1.50 s.

concave lenses are used here. they spread the light out before it reaches the convex lens in the eye, therefore letting the image focus directly on the retina. hyperopia is known to you probably as farsightedness.