Calculating Final Velocity of a Car Using Uniform Acceleration

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Homework Help Overview

The discussion revolves around calculating the final velocity of a car that accelerates uniformly over a specified distance and time. The problem involves understanding the relationship between initial velocity, final velocity, displacement, and time in the context of uniform acceleration.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply the equation for displacement but questions the negative result for final velocity. Participants raise concerns about unit consistency and the need for conversions between kilometers and meters.

Discussion Status

Participants are actively engaging in clarifying the importance of unit conversions and ensuring that all measurements are in compatible units. There is a focus on understanding the implications of using different units in calculations.

Contextual Notes

There is an emphasis on the necessity of converting distances from kilometers to meters and ensuring that time is measured in consistent units. The original poster's confusion regarding the negative final velocity suggests a potential misunderstanding of the problem setup or calculations.

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Homework Statement


A car enters the freeway with a speed of 6.4 m/s and accelerates uniformly for 3.2 km in 3.5 minutes. How fast in m/s is the car moving after this time?

Homework Equations


DeltaX=1/2(vi+vf)(DeltaT)
Displacement=1/2(initial velocity + final velocity)(Time interval)

The Attempt at a Solution


3.2=1/2(6.4+x)(3.5)
x=-4.6
? Why is this negative? What is the final velocity?
 
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It is important to be aware of which units you are using!
 
What do you mean? Do we need to convert the km to m first?
 
You need to convert everything into the same units, It only makes sense to add/subtract/cancel units which are the same.

For example, if I'm traveling 50 miles per hour, in 1 second will I have traveled 50*1=50 miles?
Of course not, because seconds are not the same as hours. (This is essentially what you did wrong.)
 

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