Physics reference frames

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A student runs an experiment with two carts on a low-friction track. As measured in the Earth reference frame, cart 1 (m = 0.57 kg ) moves from left to right at 1.0 m/s as the student walks along next to it at the same velocity. Let the +x direction be to the right.

a)What velocity v⃗ E2,i in the Earth reference frame must cart 2 (m = 0.19 kg ) have before the collision if, in the student's reference frame, cart 2 comes to rest right after the collision and cart 1 travels from right to left at 0.33 m/s?

b)What does a person standing in the Earth reference frame measure for the momentum of each cart before the collision?

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@troy132,

This is a homework problem... I don't like to do homework unless I am getting a grade. But I will help.

Let's start with this question. What is the difference between the Earth Reference Frame and the student's reference frame?

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@maxdancona,

The student is moving with the cart where as the earth is stationary to the cart

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@troy132,

Quote:

The student is moving with the cart where as the earth is stationary to the cart

This statement is from the Earth reference frame.

Let's imagine God (or a deity of your choice) is holding the cart still.... and the whole Earth is moving backwards (which is why it appears to you that the cart is moving forward).

In this case is the student moving or not?

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@maxdancona,

no it would appear that the student is stationary

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@troy132,

Ok good. So that is the Car 1 Frame of reference. The earth is moving backwards and the student isn't moving.

So how do we convert a velocity in the Student's frame to a velocity in the Earth Frame?

I think what I would do is convert all of the velocities from part to (i.e. "cart 2 at rest and cart 1 traveling from right to left at 0.33 m/s) from the Student's frame to the Earth's frame?

Do you want to give that a shot? I will tell you if you are correct or not.

After that you can use conservation of momentum to solve everything in the Earth's frame of reference.

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Physics reference frames

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