25. MAIN(Idea Describe the acceleration of your bicycle as you ride it from your home to the store.
26. Determine the change in velocity of a car that starts at rest and has
a final velocity of 20 m/s north.
27. Describe the motion of an object that has an acceleration of O m/s2
28. Think Critically Suppose a car is accelerating so that its speed is
increasing. First, describe the line that you would plot on a speed-
time graph for the motion of the car. Then describe the line that you
would plot on a distance-time graph.
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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".