# Is the Velocity negative or positive?

Member warned about re-posting the same problem statement in new threads. Infraction points awarded.

## Homework Statement

If you were to throw a large log over the edge of the Grand Canyon and it took 5.65 seconds to hit the ground, calculate the velocity of the log at impact in m/s and calculate the distance the log fell in feet.[/B]

vf=vi+at[/B]

## The Attempt at a Solution

So I get vf=(9.8)(5.65)= 55.4 ...But then I think about it, and the object is going downwards so shouldn't it's velocity be negative (South)..? Also, is 9.8 supposed to be positive or negative?[/B]

NascentOxygen
Staff Emeritus
You can choose g to be positive or negative, whichever you wish. The final velocity here will take on whatever sign you give to g. The important thing is that you remain consistent! :)

You can choose g to be positive or negative, whichever you wish. The final velocity here will take on whatever sign you give to g.

So there's always two right answers?

NascentOxygen
Staff Emeritus
So there's always two right answers?
Not really. It's final velocity is 55.4 m/s towards the centre of the Earth. That's one answer. :)

I'd be concerned about your omission of the units when talking of velocity, though.

Not really. It's final velocity is 55.4 m/s towards the centre of the Earth. That's one answer. :)

I'd be concerned about your omission of the units when talking of velocity, though.

Sorry, haha *m/s. One last question, is acceleration the same for all objects?
Well, it is, due to gravity (9.8m/s^2) ..but then again I get confused because there's so many different word problems with different accelerations as answers, obviously. What would be the final, true answer though?

NascentOxygen
Staff Emeritus