What is the Average Velocity of a Ship and the Velocity of the River Current?

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Homework Help Overview

The problem involves calculating the average velocity of a ship traveling in opposite directions with different speeds, as well as determining the velocity of the river current. The subject area pertains to kinematics and average velocity concepts.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the definition of average velocity and its relation to average speed. There are attempts to clarify the formula for average velocity and its applicability to the scenario presented.

Discussion Status

The discussion is exploring different interpretations of average velocity and the appropriate equations to use. Some participants have provided insights into the limitations of certain formulas, while others are questioning the assumptions made in the original poster's approach.

Contextual Notes

There is a mention of confusion regarding the application of the average velocity formula, specifically noting that it may not apply to the situation described, which involves varying speeds in opposite directions.

kerol9904
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Homework Statement


A ship goes from A to B at v_1=10 km/h and from B to A at v_2=16 km/h Find: (1) the average velocity of the ship, and (2) the velocity of the river current.


Homework Equations


v_{avg}=(v_1+v_2)/2
v_{AC}=v_{AB}+v_{BC}

The Attempt at a Solution


v_{Boat}-v_{Current}=10km/h
v_{Boat}+v_{Current}=16km/h
v_{Boat}=13km/h, v_{Current}=3km/h
The actual answer for v_{Boat}=12.3km/h Why is that?
 
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What's the definition of average velocity (really average speed)?
 
Change in position/Change in time?
 
kerol9904 said:
Change in position/Change in time?
Try total distance / time.

kerol9904 said:
v_{avg}=(v_1+v_2)/2
This only applies to uniformly accelerated motion, which is not what's going on here.
 
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Ahh... I didn't realize that the equation is only for uniformly accelerated motion. I've got the answer now. Thanks!
 

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