You start out on a trip by driving in a straight line at a constant speed of 20

Question

You start out on a trip by driving in a straight line at a constant speed of 20 m/s for 15 seconds. You are driving along the x axis, in the positive direction.
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1.What is your average velocity for this part of the trip?
2. What is your displacement during this part of the trip?
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Next you start to speed up, accelerating at a constant rate of 2 m/s2 for the next 15 seconds.
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3.What is your final velocity?
4.What is your displacement during this part of the trip?

Now suppose instead that at the end of the first part of your trip (at constant speed), you see a truck ahead of you, blocking the road. You immediately start decelerating, with a constant acceleration of -2 m/s2.
5.How far away must the truck be so that you do not hit it?

Explanation / Answer

1. Constant velocity, hence 20m/s

2. Displacement : 20x15= 300m

3. v = u + at

v = 20 + 15 x 2 = 50m/s

4. s = ut + 0.5 at2 = 20x15 + 0.5 x 2 x (15)2 =525m

5. v2 = u2 +2as

v = 0

u = 50

s = (50)2 / 2 x 2 = 625m

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