How do I find the velocity in this momentum conservation problem?

[Turhan]

Homework Statement

A 60 kg farmer ropes a 300 kg ox. Both are initially at rest, 24 m apart on a frictionless level surface. When farmer ends up pulling the ox towards him, the ox will move

A) 4m, B) 5m, C) 12m, D) 20m, E) 24m .
Can anyone help me solve this?

Homework Equations

The Attempt at a Solution

 

[billy_joule]

We can help, but you need to make some effort first.

Check your notes and textbook.
Or these should get you started:
http://www.physicsclassroom.com/class/momentum/Lesson-2/Momentum-Conservation-Principle
http://hyperphysics.phy-astr.gsu.edu/hbase/conser.html#conmom

 

[Turhan]

Okay so in the momentum eq, how do I find out the velocity?

 

[billy_joule]

You can't find the magnitude of the velocity of either the farmer or the Ox.
But you don't need to.. You only need to find the ratio of the velocities.
Show us your attempt and we'll see where you're stuck.

 

[PeroK]

Homework Statement

A 60 kg farmer ropes a 300 kg ox. Both are initially at rest, 24 m apart on a frictionless level surface. When farmer ends up pulling the ox towards him, the ox will move

A) 4m, B) 5m, C) 12m, D) 20m, E) 24m .
Can anyone help me solve this?

Homework Equations

The Attempt at a Solution

In my opinion, this is one of these silly questions that makes no real sense. You have to know what practical elements the questioner intends you to ignore and what elements to focus on. Physics is supposed to model the real world, but an absurd question like this blatantly ignores the practical realities.

Anyway, you are supposed to concentrate on conservation of momentum. But, once something has momentum on a frictionless surface, it's not going to stop. So, you are supposed to assume that the farmer and ox move very slowly and bump into each other and stop. So, the question is asking how far the ox has moved when they bump into each other.

 

[Turhan]

In my opinion, this is one of these silly questions that makes no real sense. You have to know what practical elements the questioner intends you to ignore and what elements to focus on. Physics is supposed to model the real world, but an absurd question like this blatantly ignores the practical realities.

Anyway, you are supposed to concentrate on conservation of momentum. But, once something has momentum on a frictionless surface, it's not going to stop. So, you are supposed to assume that the farmer and ox move very slowly and bump into each other and stop. So, the question is asking how far the ox has moved when they bump into each other.

How am I supposed to find the velocity? This is question from a previous regional olympiad phase.

 

[PeroK]

How am I supposed to find the velocity? This is question from a previous regional olympiad phase.

The velocity is not relevant. That's one of the things you are supposed to know from reading the question.

 

[haruspex]

you are supposed to assume that the farmer and ox move very slowly

The speed does not matter for the answer, though I suspect it would matter to the farmer.

 

[haruspex]

How am I supposed to find the velocity

Write out the momentum conservation equation, and think of it as a differential equation.