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Question

Brad is working on a speed problem in physics class. The problem tells him that a girl runs from her house to the park 0.05 km away in 10 s. Brad calculates that her speed is 0.005 m/s. Is he correct? If not, explain the flaw or flaws in his problem solving process.

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Answer 1 · 2018-03-10T22:11:45

no

$0.05km = 0.05 * 1000m$

$= 50m$

$s = d/t$

where $d$ is distance in metres $m$ ,

$t$ is time in seconds $s$ ,

and $s$ is speed in metres per second $m//s$ .

here, $d = 50m$ and $t = 10s$

$d/t = 50/10$

$s = 5 m//s$

the speed could also be expressed as $0.005 km//s$ , but not $5 m//s$ ;

the number would need to be multiplied by $1000$ since the unit $km$ was converted to $m$ .