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January 28, 2015

January 28, 2015

Posted by **mattie** on Tuesday, August 31, 2010 at 9:28pm.

(a) What is her average speed over the entire trip?

- physics -
**drwls**, Tuesday, August 31, 2010 at 10:33pmIt is not the average of 4.9 and 2.7, because she spends more time walking at the slower speed.

Let the total distance between A and B be D

t1 = D/4.9 t2 = D/2.7

Average speed = 2D/*t1 + t2)

= 2D/[(D/4.9) + (D/2.7)]

= 2/[(1/4.9) + 1/(2.7)] = 3.38 m/s

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