Any question answered...

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  • Why would a physical string be taut if you cut the ball off? I don't think that would work in practice.

    I agree that the non-tangent component of the ball's momentum is where the centrifugal bit comes from, there's no magic. They're just labelling it "centrifugal" because it acts in that direction.

    I think you're missing the mark with the balanced forces though, that's not what the 3rd law means. Equal and opposite forces can also mean two objects accelerating away from each other.

    In this case the acceleration on the ball should ultimately match an imperceptible change in the Earth's wobble, communicated from the string, to the post, to the ground.

    If one of those forces, say the force exerted by the post on the ground, is not matched in the 3rd law sense - it just means you have a wobbly post.

  • I'm suspicious of this ball and string. If you cut the ball off, a physical string would still be taut.

    Sort of. The point of a ball on the end of a string is that you can simplify the system and ignore the elasticity of a string, air resistance, etc. It's a point mass (the ball) on the end of a light inelastic string.

    If you take away the ball then you have to come up with something that is the mass at the end of the string. The natural thing would be to consider splitting the string into two halves, and that the half furthest from the anchor point is a mass that replaces the ball for the sake of the setup.

  • Why would a physical string be taut if you cut the ball off? I don't think that would work in practice.

    Because it has mass and thus intertia.

    the non-tangent component of the ball's momentum is where the centrifugal bit comes from, there's no magic. They're just labelling it "centrifugal" because it acts in that direction.

    It's completely tangential though. The apparent centrifugal force is surely a consequence of making forces neatly balance to zero in a non-inertial reference frame so you can worry about other aspects. It just doesn't exist in the inertial frame.

    In this case the acceleration on the ball should ultimately match an imperceptible change in the Earth's wobble, communicated from the string, to the post, to the ground.

    But then the model is better described as two masses, ball and earth (or ball and wobbly post), and we might as well have a massless string connecting them. The system rotates around a point on the string. Still simplifies to a single rotating mass.

  • Flat roofs need a parapet wall around the edge, high enough to stop heavy rain bouncing over the front edge and down the wall. You can do away with that if you have a visible gutter on the front.

  • Sort of. The point of a ball on the end of a string is that you can simplify the system and ignore the elasticity of a string, air resistance, etc. It's a point mass (the ball) on the end of a light inelastic string.

    But if I recall my ancient physics A level, normally model strings are massless and transmit forces between masses. This model doesn't seem to follow this convention by having a string with mass - what's the physicist's equivalent to a programmer's 'code smell'?

    If you take away the ball then you have to come up with something that is the mass at the end of the string. The natural thing would be to consider splitting the string into two halves

    This seems to complicate rather than simplify and again- why not model the whole thing as a single rotating body? I think it's wrong to think of an 'anchor point' in the inertial frame, it's just the centre of rotation of the system, where there are no resultant forces - can't be, as it's not moving.

    The natural thing would be to consider splitting the string into two halves, and that the half furthest from the anchor point is a mass that replaces the ball for the sake of the setup.

    I suspect this is a trap - as soon as you start focusing on components of the system, you are constructing a non-inertial frame.

  • A single rotating solid mass probably consists of at least two atoms acting on each other with - wait for it - equal and opposite electrostatic forces. Chopping and changing your component definitions doesn't alter anything.

  • Can these forces be used for pleasure?

    Depends if you enjoy a good game of Swingball.

  • It was a filter in between the bucket and the motor unit.

  • What about George and James?

  • They're trains.

  • They other numatic named vacuums.

    But Thomas the tank engine taught me everything about people.

  • Who / what was the audio book streaming service that had a thread on here last year?

  • I need some new brake pads. Is it worth looking at anything over then Shimano B05s? (Has to be the same shape obviously).

  • I very rarely by oe pads, I.e desperate and need the pads straight away, and just buy a few packs from Uber bikes when needed, never had any issues with them.

    https://www.uberbikecomponents.com/category/337/Shimano-Disc-Brake-Pads

  • I’m pretty impressed with the Gorilla pads that were recommended on here. No squealing in the wet so far which makes them 100% better than the shimano pads they replaced

  • Where can I get these lamps in the UK, my Google fu seems to have totally failed me

  • Does anyone have experience of employers of record from an employee perspective?

    I just did a first interview with a company of around 500 employees for a remote role, fairly senior. If successful I'd be coming from a huge multinational with entities and offices in most countries. The interviewer was very keen to tell me that they don't currently have many staff in the UK, so I'd be technically employed by an employer of record (EOR), and wanted to check I was okay with that.

    I was honest and said that I didn't really know what that means, but would look it up after the interview and let them know if I was concerned.

    After searching around, I now understand the concept. However, I want to make sure I'm not putting myself at any risk. All the articles about risk that I've found are so far centred on the risk to the employer, not the employee.

    Just looking to understand if there's anything I should be wary of or ask specifically about for this type of arrangement.

  • I want to make sure I'm not putting myself at any risk

    I think you are compared to working directly for a UK company in some situations, for example redundancy where you appear to have fewer rights eg during a consultation process. That might not worry you much.

    I'd want to check for any tax issues, probably fine if the EOR is running PAYE.

  • Thank you! I will keep researching more, and perhaps seek some professional advice from an employment solicitor if i get a job offer.

  • Thanks! (and thanks to @kilo24). I decided to splash out on the Gorilla pads.

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Any question answered...

Posted by Avatar for carson @carson

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