What Height Was the Baseball Dropped From Based on Its Momentum?

[alyson42]

Homework Statement

A .150kg baseball is dropped from rest. IF the magnitude of the baseball's momentum is .780 kg m/s just before it lands on the ground, from what height was it dropped?

Homework Equations

P=mv

The Attempt at a Solution

I found the final velocity and know that the inital position is zero and the initial velocity is zero obviously. i tried to go back to the kinematic equations to solve for final position but i do not know time and i do not know acceleration.

 

[dirk_mec1]

Use an energy balance and choose you title with care please...

 

[alyson42]

energy balance?

 

[alphysicist]

Hi alyson42,

Homework Statement

A .150kg baseball is dropped from rest. IF the magnitude of the baseball's momentum is .780 kg m/s just before it lands on the ground, from what height was it dropped?

Homework Equations

P=mv

The Attempt at a Solution

I found the final velocity and know that the inital position is zero and the initial velocity is zero obviously. i tried to go back to the kinematic equations to solve for final position but i do not know time and i do not know acceleration.

You don't know the time, but are you sure you don't know the acceleration?

 

[alyson42]

acceleration due to gravity? just 9.81 m/s? can it be that easy?

 

[alphysicist]

Sounds good; your acceleration units aren't quite right, but maybe that's just a typo. Depending on how you set up the problem you might need to be careful with signs, but it seems to be a straightforward problem.

 

[alyson42]

i got the correct answer. You are a genius. Thanks for the help!