Acceleration question -- Deceleration of a baseball being caught by a player

[Rasofia]

1. A baseball is traveling at +18 m/s and is caught by a player. The ball is brought to rest in 0.5 s. What is the acceleration of the ball?

Homework Equations

Maybe vf=vi+ at ?

The Attempt at a Solution

This is under a Horizontal Projectiles worksheet by the way...I'm not sure what to do on this one though. At first I thought to use the equation above and make 18 the final velocity since that's how it's caught...but then what would be the initial? So then I thought...okay maybe the initial could be 18 and the final is 0 since it says 'at rest'. I don't know, this is a bit complicated. Well, If I do it the second way, I get 36 m/s^2

 

[SteamKing]

1. A baseball is traveling at +18 m/s and is caught by a player. The ball is brought to rest in 0.5 s. What is the acceleration of the ball?

Homework Equations

Maybe vf=vi+ at ?[/B]

The Attempt at a Solution

This is under a Horizontal Projectiles worksheet by the way...I'm not sure what to do on this one though. At first I thought to use the equation above and make 18 the final velocity since that's how it's caught...but then what would be the initial? So then I thought...okay maybe the initial could be 18 and the final is 0 since it says 'at rest'. I don't know, this is a bit complicated. Well, If I do it the second way, I get 36 m/s^2[/B]

When you catch a ball in a glove, how fast is it going when it comes to rest?

Is the catcher flung backwards by the ball he has caught?

When you are at rest on your couch, do you have any velocity?

This problem is complicated only because you are over thinking it.

 

[Rasofia]

When you catch a ball in a glove, how fast is it going when it comes to rest?

Is the catcher flung backwards by the ball he has caught?

When you are at rest on your couch, do you have any velocity?

This problem is complicated only because you are over thinking it.

so I'm right, it's 36?

 

[SteamKing]

so I'm right, it's 36?

It appears to be so.

 

[haruspex]

so I'm right, it's 36?

Not quite. The initial speed is carefully stated as "+18m/s". If you plug that in as v_i in your "relevant equation" and put v_f=0, what exactly do you get for a?