A high school athlete runs #1.00 * 10^2# #m# in #12.20# #s#. What is the velocity in #m##/##s# and #km##/##h#?

1 Answer
Eric C.
Jul 6, 2016

#8.20ms^-1# (3sf) and #29.5kmh^-1# (3sf)

Explanation:

In order to calculate the velocity we need both the distance travelled and the time taken to travel that distance. In this case we have both, I will start by converting the #1.00# x #10^2# into standard form which is #100#m

So #v = d/t#

#d = 100m# & #t = 12.20s#

Substitute both these values into the equation:

#v = d/t = (100m)/(12.20s) = 8.20ms^-1#

I like to keep the units in the calculation to make working the units of velocity out easier.

Now we know the velocity in #ms^-1#. To calculate the speed in #kmh^-1# we need to convert both the #m# & #s#, this can be done in multiple ways. However we know that #1000m# = #1km# and #1#hour = #3600#seconds.

Therefore we need to multiply our answer by: #(1000m)/(3600s)# So...

#v = 8.20ms^-1# x#3.6 = 29.5kmh^-1#

Note: I retained the non-rounded value in the calculator through the calculations, this will improve your accuracy and avoid rounding error.

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