Find velocity and acceleration (positive or negative)

[Kerrie yu]

What would the velocity and acceleration be if a person was tossing a ball upward but downward direction is positive? When the ball was falling down, what would the velocity and acceleration be?

 

[KurtWagner]

On the way up, your acceleration would be down (positive) and your velocity would be up (negative).

Once the ball is falling, the acceleration is still down (positive) and the velocity is down (positive)

 

[KurtWagner]

... Assuming there is gravity

 

[Kerrie yu]

But wouldn't there be a difference since the downward direction is positive

 

[Kerrie yu]

Oh wait,,, nvmm thxx

 

[KurtWagner]

Its also cool to note that even at the top of the motion, when the velocity is zero, the acceleration is still in the down (positive) direction.

 

[Kerrie yu]

Oh yea,, its something like the acceleration cannot be 0 because if it is , it againsts the gravity ...something like that..right?

 

[KurtWagner]

Gravity is always accelerating the object. But the object has to stop before going backward (has to be 0 velocity). This is a really really really small time though.

 

[CWatters]

What would the velocity and acceleration be if a person was tossing a ball upward but downward direction is positive?

I assume you are talking about what happens after it leaves the mans hand while subject to gravity (eg not while he's actually throwing it).

On the way up...

The displacement is negative
The velocity is negative
The acceleration is positive

When the ball was falling down, what would the velocity and acceleration be?

After max height on the way down...

The displacement is initially still negative but then it goes positive as it passes the origin.
The velocity is positive
The acceleration is positive