Homework Help: Science

Posted by Becca on Friday, September 30, 2011 at 4:49pm.

The problem I'm trying to answer is:
Ann is driving down a street at 59 km/h.
Suddenly a child runs into the street.
If it takes Ann 0.719 s to react and apply
the brakes, how far will she have moved before
she begins to slow down?
Answer in units of m.

I know the first step is to convert 59 km/h to m/s, but I'm not sure how. I know how to solve the problem after ward. Can someone show me and explain the formula I would need to use for this problem? Thank you!

Science - Steve, Friday, September 30, 2011 at 5:26pm
To convert units, just remember that multiplying by one does not change anything. You just have to pick the way of writing 1 that gets you what you want. You do this all the time, without consciously following the logic. In this case, we have

59km/h * 1000m/km * h/3600s = 16.39m/s

Now, to convert this to meters, just multiply by seconds, so they disappear form the fraction:

1.39m/s * 0.719s = 11.784m

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