Two boxes are tied together by a string and are sitting at rest on a frictionless surface

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Video Transcript

Okay, so here we have a situation whether two blocks connected by a spring on a small light string on that like string snaps, sending the two masses in opposite directions. Now, before anything happens, we have a total mental off zero. So it's right. Peanuts equals zero. So total months was going to be zero. Which means that in our second situation, um, one will be one final plus. And to be to final has to equal to zero. Now we know that the massive the larger object is three am in amassed. A small object is just so and the one plus three and me too, is equal to zero. The lodge, a block, has a mass of two meters per second going to the right. So now we know and the one plus 6 a.m. equals zero so that we could just rearrange remove the EMS. We can see that V one is equal to negative six. I had meters per second. It is moving to the left at six meters per second. All right, Poppy, I want to find the original amount of elastic potential energy. So we find the mass is 0.35 kilograms. Let's find the elastic potential energy. Knowing that energy is conserved, we should know that the final kinetic energy is equal to the initial elastic potential energy on the question friend. If a kinetic energy is 1/2 times mass times velocity squared. So substituting in numbers for both of our blocks. 1/2 times point 0.35 Terms of velocity of that first block, which is negative six squared plus 1/2 times three times 30.35 times a velocity of that one, which was two squat. Concluding that out, you'll find that the total kinetic energy and therefore the amount of elastic potential energy start in the spring is eight point full. Jules. So is the energy stored in the spring or the card. While the court doesn't still any energy, it doesn't have the ability to do work on the object. So the only thing able to store the energy is the spring. Unlike I said, work is done on the spring, which allows it to store the energy. The card exerts a force, but it doesn't exert that force over a specific distance. Now momentum here is conserved. Even though we have large forces acting in our system. They're all within the system. So the forces are all internal because all the forces air internal. That's not going to affect our overall momentum off the system. And again, there's plenty of motion after the card breaks in the spring pushes those blocks, and there's no momentum before while it's storing that energy. But the momentum is conserved because they go in opposite directions. The mass multiplied by the velocity is what we're looking at in terms of momentum. Now the small block moves to the left in a large block, moves to the rights, but they move with equal momenta and different velocities. It's equal in magnitude but opposites in direction, so the mountain is conserved. It's equal in magnitude, but opposite in direction. Even though the forces are all internal, that doesn't affect the momentum of our system.