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Homework Help: No idea (velocity)

  1. Sep 16, 2007 #1
    1. The problem statement, all variables and given/known data
    car moving 12.0m/sec eastward on straight road. inside car, bug is flying eastward at 2.0m/s relative to the car. how fast is the bug moving relative to the road? repeat for the bug moving westward.

    2. Relevant equations

    3. The attempt at a solution

    i assume the westward movement will be a negative ratio
  2. jcsd
  3. Sep 16, 2007 #2
    You know how relative velocity works?

    Its like this:

    V1(Relative velocity of body 'a' wrt to body 'b') = V2(Velocity of body 'a' wrt ground) -
    V3(Velocity of body 'b' wrt ground)

    Yes the westward movement will be -ve quantity if u take the eastward motion of car as +ve.
    Last edited: Sep 16, 2007
  4. Sep 16, 2007 #3
    what about average acceleration? is that distance/time?
  5. Sep 16, 2007 #4


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    Homework Helper

    Change in displacement over time is velocity. Changes in velocity over time is acceleration.

    Average acceleration is the average acceleration over a period of time, say t1 (10.30am) and t2 (10.32am). Then if the velocity v1 at t1 was 40km/hr and the velocity v2 at time t2 was 30km/hr, the average acceleration would be:

    (v2-v1) divided by (t2-t1) = (-10km/hr) per (2 mins) = -5 km/hr per min
    which is interpreted as a slow down of 5km/hr in velocity every minute, over the past 2 minutes.
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