ice block physics question?

[Fighter127]

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A 10 kg block of ice is sliding due east at 8.00 m/s when it collides elastically with a 6 kg block of ice that is sliding in the same direction at 4.00 m/s. Determine the velocities of the blocks of ice after the collision.

 

[Cawolf]

Yes, this is a question - what is your question?

I'll give you a hint - solve for the initial momentum of both objects (taking velocity as a vector into account) then solve by conservation of momentum.

 

[justadream]

@Cawolf
I'm also curious about how to do this question.

Once you get the initial momentum, how do you solve for the two final velocities?

Don't you need to use a second equation or something?

 

[Cawolf]

Conservation of energy (you are told it's an elastic collision).

I could work it out of course, but for posts like this they might as well just check their answer key.

 

[Fighter127]

Yes, this is a question - what is your question?

I'll give you a hint - solve for the initial momentum of both objects (taking velocity as a vector into account) then solve by conservation of momentum.

Sorry i should have said that earlier, I tried using the conservation of momentum: Pinitial=Pfinal, to solve for the final velocities of both ice blocks, but I get stuck because since its an elastic collision there are two different final speeds (one for each block) leaving two unknowns. I don't know which information im missing or if there's another equation i need to use to create a system of equations.

 

[Cawolf]

It's generally a really long problem to solve with tons of algebra - the second equation is conservation of energy.

 

[Cawolf]

This isn't a MCAT question right? Because I don't know of a shortcut to solve it.

 

[justadream]

@Cawolf

Oh right, yes.

I think there are some shortcut equations but I forgot them. I've only seen inelastic collisions show up on AAMC questions.

 

[Cawolf]

I hope so, because problems like this take me at least 15 minutes to solve with all the mess of algebra.

If there were shortcuts, I don't know them yet at least.

That's good to hear.

 

[justadream]

@Cawolf

Here are the equations. They used conservation of energy to derive them. However, they only apply when object 2 is initially at rest (not the case here).

 

[Cawolf]

Right, that's what makes this problem long.