Calculating Final Velocity of a Car Using Uniform Acceleration

AI Thread Summary
To calculate the final velocity of a car accelerating uniformly, the initial speed is 6.4 m/s, and the car travels 3.2 km in 3.5 minutes. The equation used is DeltaX=1/2(vi+vf)(DeltaT), but the units must be consistent for accurate results. A conversion from kilometers to meters and minutes to seconds is necessary to avoid negative values in calculations. The discussion highlights the importance of unit conversion in physics problems to ensure correct outcomes. Proper unit management is crucial for determining the final velocity accurately.
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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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