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course Phy 241
7/12/2013 6:25 pm
What are the average acceleration and final velocity of an object which accelerates uniformly from rest, attaining a velocity of 40 cm/sec in 13.6 seconds? How far does the object travel during the 13.6 seconds?
vAve = 40cm/s/13.6s ≈ 2.9412 m/s
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40 cm/s / (13.6 s) does not have units of m/s, nor does it have units of cm/s.
This calculation doesn't have units of velocity, and doesn't represent a velocity.
What does 40 cm/s represent?
What does it mean to divide this quantity by the time interval?
What are the units of the result?
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final velocity ≈ 5.8823 m/s
object travels 544 m"
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Moving at 40 m/s for 13.6 sec an object would move 544 m.
However this object doesn't move at 40 m/s for 13.6 s. It starts from rest and only attains that speed at the very last instant of the interval.
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You have some relevant calculations, but some are misidentified, and some are incorrect.
You need to carefully apply the definitions of velocity and acceleration, and calculate your units by doing the algebra of the units.
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