A baseball is thrown from the outfield toward the home plate

[Apple]

1. The problem statement, all variables, and given/known data
A baseball is thrown from the outfield toward the home plate. a) Neglecting air resistance, is the momentum of the ball conserved during its flight? explain b) Neglecting the air resistance, is the momentum of the earth-ball system conserved during baseball’s flight? explain.

Homework Equations

3. The Attempt at a Solution [/B]
I think the statement in part A is false and part B is true, I just don't know if I'm am right please explain the answers. Thank in advance!

 

[Ray Vickson]

1. The problem statement, all variables, and given/known data
A baseball is thrown from the outfield toward the home plate. a) Neglecting air resistance, is the momentum of the ball conserved during its flight? explain b) Neglecting the air resistance, is the momentum of the earth-ball system conserved during baseball’s flight? explain.

Homework Equations

3. The Attempt at a Solution [/B]
I think the statement in part A is false and part B is true, I just don't know if I'm am right please explain the answers. Thank in advance!

We are not allowed to "explain the answers"; we are just allowed to offer hints. Surely you know why you gave those answers. What were your reasons?

 

[Apple]

We are not allowed to "explain the answers"; we are just allowed to offer hints. Surely you know why you gave those answers. What were your reasons?

I assumed that there were no external forces since air resistance was neglected. So, when no external forces act on an object the total momentum is constant. The Earth in the system causes the external force (mg) to become internal to the system and is canceled out by the third law force pair of the gravitational force of the ball on the earth.Then there would be no more outside force that would be able to change the kinetic energy.

 

[PeroK]

I assumed that there were no external forces since air resistance was neglected. So, when no external forces act on an object the total momentum is constant. The Earth in the system causes the external force (mg) to become internal to the system and is canceled out by the third law force pair of the gravitational force of the ball on the earth.Then there would be no more outside force that would be able to change the kinetic energy.

I can't actually make out from that what your answers are. Try, instead:

In a) momentum is conserved/not conserved [delete as applicable] because ...

 

[Apple]

I can't actually make out from that what your answers are. Try, instead:

In a) momentum is conserved/not conserved [delete as applicable] because ...

In a) momentum is not conserved because if there is an outside force acting on the ball (Gravity is an external force).
In b) momentum is conserved when the earth-ball system has no net momentum its final and initial momentum is the same, therefore it is constant.

 

[PeroK]

In a) momentum is not conserved because if there is an outside force acting on the ball (Gravity is an external force).
In b) momentum is conserved when the earth-ball system has no net momentum its final and initial momentum is the same, therefore it is constant.

I think you've got the idea, although for b) you seem to have expressed things in an odd way. Did you think about using the term "internal forces" or "Newton's third law"?

That said, question b) is a bit odd, in that it mentions air resistance. That seems odd to me, because if you take the atmosphere out of the system, then the (solid) Earth and the ball are no longer a closed system. But, if the air is part of the Earth, then you have a closed system.