physical doubt? ?

[Wolverine]

Hello, everyone!
I have a doubt.
if I have a body that moves motion evenly accelerated with negative acceleration (so the body is slowing down with constant acceleration), if I want to know the speed at a certain instant v=a*t.ma if to is negative as in this case, should v not come negative from the formula? Yet the speed decreases module but does not change direction, so it should remain positive, right? then why from the formula gives me the negative sign?

Thank you! !

 

[davide75]

http://www.openfisica.com/fisica_ipertesto/intro/legge_moto_accelerato.php

 

[cacciatorino]

Hello, everyone!
I have a doubt.
if I have a body that moves motion evenly accelerated with negative acceleration (so the body is slowing down with constant acceleration), if I want to know the speed at a certain instant v=a*t.ma if to is negative as in this case, should v not come negative from the formula? Yet the speed decreases module but does not change direction, so it should remain positive, right? then why from the formula gives me the negative sign?

Thank you! !

because you have to consider the initial speed:

v(t1) = vo - a*t1

where the speed is at the beginning of the braking. Until then the value of v(t) > 0. But there's a moment when vo < a*t which is the moment when the body begins to reverse.

 

[Wolverine]

thank you 1000 of the answer!.. now I understand!

Bye!