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What do you think, please?

  1. Sep 17, 2009 #1

    a2n

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    What do you think, please???

    1. The problem statement, all variables and given/known data

    Here it is:
    Starting from rest at point A, you ride your motorcycle north to point B 75m away, increasing speed at steady rate of 2 m/s2. you then gradually turn toward the east along a circular path of radius 50m at constant speed from B to point C until your direction of motion is due east at C. you then continue eastward, slowing at a steady rate of 1m/s2 until you come to rest at point D.
    a. what is your average velocity and acceleration for the trip from A to D?
    b. What is your displacement during your trip from A to C?
    c. What distance did you travel for the entire trip from A to D?


    2. Relevant equations
    V ave = r/t
    Vot+(1/2)at2
    2(Pi)r


    3. The attempt at a solution

    Thanks...
     
    Last edited: Sep 17, 2009
  2. jcsd
  3. Sep 17, 2009 #2
    Re: What do you think, please???

    Well, a hint for the average velocity is to find the total distance and total time. As for the displacement, I haven't done much calculation on such things but I would try to see it as a coordinate system with A in (0, 0). And the last one you should already have calculated by now, just do each part by itself and add.

    This is introductory physics I believe
     
  4. Sep 17, 2009 #3

    HallsofIvy

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    Staff Emeritus
    Science Advisor

    Re: What do you think, please???

    Have you plotted the path? In particular, where is point B? Once you have that, point C is exactly 100 m east of B. Since he accelerated at 2 m/s^2 you should be able to find t such that (1/2)(2)t^2= 75 m and then v= 2t to find his speed at B. Since he goes around the circle at that speed, you can divide the circumference of the (half) circle by his speed to find the time he arrives at C. Then you can calculate the time required to slow 1 m/s^2 to 0 and then calculate how far he went south to find point D.

    What is the straight line distance between A and D? How much time did he take to go from A to D? The "average velocity" is the distance divided by the time. Since he started and ended motionless, the "average acceleration" is trivial!

    Notice that the "straight line distance between A and D" is NOT "the distance traveled for the entire trip" which is the distance from A to B plus the circumference of the half circle from B to C plus the distance from C to D.
     
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