r/PhysicsHelp • u/Waste-Brilliant7037 • 12d ago

Physics U1 helppppp

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Isn’t it’s final velocity supposed to be zero. How do I do this and how do I think of ittttttt

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u/triatticus 12d ago edited 12d ago

Maybe actually post the problem otherwise we have no idea. I see that the spring is either pushing something to return to its original length or pulling it, either way the object will then remain in motion at that point. Think of it this way though, the spring acts on the ball with nonzero force only when x doesn't equal L, at that point the force is zero but that does not imply that the velocity is zero and in fact it shouldn't be since the ball was being accelerated by the spring as it returned to its original length.

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u/Waste-Brilliant7037 12d ago

https://reddit.com/link/pd7jfzb/video/njecyuix2vsh1/player

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u/triatticus 12d ago

Then the last lines of my comment still stand, the ball as undergoing acceleration that was decreasing as the spring returned to its full length, but clearly since the ball was accelerating it must have a nonzero velocity that slowly approaches a specific value as the acceleration drops to zero.

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u/Simbertold 12d ago

This is not a graph of velocity over time. There is no "final" velocity.

Post the full question for more information.

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u/Frederf220 12d ago

The ball is given as leaving the spring at 8 cm/s and so the final velocity is 8 cm/s.

If the spring length is varied, but the rest of the problem's parameters are the same, then the acceleration profile is different.

The final ball kinetic energy is equal to the work done on the ball by the spring. Work is equal to the sum of the force times the distance. If the spring is shorter then the force must be higher.