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Unit conversion between two compound units.

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A Cheetah runs at a speed of {speedkm} kilometres per hour (km/h). What is the Cheetah's speed in metres per second (m/s)?

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Give your ansswer to 2 decimal places where appropriate.

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There are a number of ways to work out the conversion. Here are a couple of suggestions.

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METHOD 1

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Since there are $1000$m in $1$km we first multiply by $1000$ to get the speed in metres per hour:

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\\begin{equation} 1000*\\var{speedkm} = \\var{step1}\\end{equation}

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Then we divide by $3600$ since that is the number of seconds in an hour to get the speed in metres per second:

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\\begin{equation} \\frac{\\var{step1}}{3600} = \\var{speedms} \\end{equation}

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Finally we round off to 2 decimal places as required, $\\var{roundanswer}$m/s.

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METHOD 2

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We can actually do all of the above in one step of working by using a single conversion factor. Since there are $1000$m in a km and $3600$ seconds in an hour, we can calaculate the conversion factor:

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\\begin{equation} \\frac{3600}{1000} = 3.6 \\end{equation}

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and then simply divide by that conversion factor:

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\\begin{equation} \\frac{\\var{speedkm}}{3.6} = \\var{speedms} \\end{equation}

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finally rounding off as before, $\\var{roundanswer}$m/s.

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Use this link to find some resources which will help you revise this topic.

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[[0]]m/s

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