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Q & A: units of length

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Most recent answer: 09/22/2011
Q:
Why do some projectile motion equations use -16t squared and some use -9.8t squared
- Nick (age 15)
Glenolden, PA, USA
A:
You're talking about changes in height due to gravity. Neither of those expressions are correct, since they do not include units of length or time. The first would be

h= - 0.5*32 feet/s2 *time2

The second would be
h= -0.5*9.8 meter/s2 *time2

I'm not sure why one of the versions you gave included the factor of 0.5 and the other didn't.

Mike W.

(published on 09/22/2011)

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