## Inertia in Linear and Rotational motion?

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Boris Lagutin
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Location: USA

### Re: Inertia in Linear and Rotational motion?

Even though you had already given me this link time in which you give me is appropriate
Boris Lagutin
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Boris Lagutin
Posts: 178
Joined: Thu Aug 28, 2014 9:17 pm
Location: USA

### Re: Inertia in Linear and Rotational motion?

Let me assume a string and a ball connected with the spring. So if we rotate the system "ball-spring" around some center we get circular motion (no matter which plane (vertical, horizontal, tilted). Let's take a vertical plane so we have: T + mg = ma, hence T = m*(a - g). Then T = 0 when a = g (weightlessness of object). In this case if centripetal acceleration "a" goes to infinity it means that T increases (doesn't matter in which plane we rotate). If I don't mistake it looks like: plane of rotation has some relations of relativity with a vector (coming from center) of gravitational field? In other words, it depends on which angle is between the rotation plane and a gravity field radius I don't know how to express. I have not learnt gravity fields yet.
Boris Lagutin
student

Boris Lagutin
Posts: 178
Joined: Thu Aug 28, 2014 9:17 pm
Location: USA

### Re: Inertia in Linear and Rotational motion?

To clarify my previous post I want to say the following. If we rotate the system in a vertical plane the equation is true: T + mg = ma (on the top of circular motion). Moreover, the state of weightlessness may be not only at the top. So if we rotate strongly enough we can get the state at other points around the top. However, if we rotates the system at a tilted plane with respect to the Earth this equation changes. Could someone explain how the equation changes? Clearly we additionally get x-components in this equation. But it's a circular motion so far. I suspect x and y components are not enough here, right?

Thank you.
Boris Lagutin
student

joe
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### Re: Inertia in Linear and Rotational motion?

For the rotation about an inclined axis, you'll need to specify components in all three dimensions.
Also, you need to be careful about two things:
- if the mass is on a spring, rather than an inextensible string, then its path will not be circular: the spring will be longer at the bottom.
- in the absence of other forces, it will not be uniform circular motion: it will travel fastest at the bottom.
So it will be a complicated problem.

Boris Lagutin
Posts: 178
Joined: Thu Aug 28, 2014 9:17 pm
Location: USA

### Re: Inertia in Linear and Rotational motion?

Thanks a lot, Joe.
Boris Lagutin
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IbnHoor
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### Re: Inertia in Linear and Rotational motion?

What makes the object go at the tangent direction (tangent velocity direction) after being released?

Newton's first law of motion.

Thank you very much Joe for your info about latest technology on School of Physics Local Data Biz
Last edited by IbnHoor on Mon Oct 09, 2017 4:59 pm, edited 2 times in total.

Boris Lagutin
Posts: 178
Joined: Thu Aug 28, 2014 9:17 pm
Location: USA

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Boris Lagutin
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