hi , with the free fall equation, in my book it is refererd to as either 4.9^2 or -4.9^2 , so which one is right, very confused

Dave

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- Mar 24th 2012, 02:37 PMdavellew69free fall equation
hi , with the free fall equation, in my book it is refererd to as either 4.9^2 or -4.9^2 , so which one is right, very confused

Dave - Mar 24th 2012, 03:11 PMSpringFan25Re: free fall equation
you choose the "positive" direction at the start of every calculation, so either can be correct.

if you choose "up" as the positive direction, then accelleration due to gravity is $\displaystyle -4.9 m/s^2$

if you choose "down" as the positive direction, then accelleration due to gravity is $\displaystyle 4.9 m/s^2$ - Mar 24th 2012, 03:13 PMdavellew69Re: free fall equation
what is ment by up or down as the positive direction?

thanks for your reply - Mar 24th 2012, 03:16 PMSpringFan25Re: free fall equation
the direction which you have to be travelling in to have a positive velocity.

so if "down" is the positive direction, and an object is falling from the top of a building, it will have a positive velocity. - Mar 24th 2012, 03:18 PMdavellew69Re: free fall equation
thanks , that simple .thank you for your time

Dave