Is spin the same as torque in physics?

In summary, the conversation discusses torque and Newton's second law in relation to a spinning object. It is established that torque is present when a force acts upon an object and changes its rotation, and that Newton's second law applies to this situation. However, it is noted that torque and angular acceleration are both vectors, and the moment of inertia is defined with respect to an axis. The conversation also mentions the possibility of nutation and precession in a spinning top, and the assumption that the axis of rotation remains constant.
  • #1
tucky
30
0
Hi everyone this is hopefully a quick and easy question:

If a person spins an object that rotates, is that considered torque?

When that object that is rotating, are the forces that act upon it: gravity, air resistance, friction, and the beginning twist from that person, Newton’s second law?
 
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  • #2
If a force acts upon an object so that the object's rotation changes, then the torque is
T = dL/dt.
So, if the person speeds up the object's rotation then, yes, there is a nonzero torque.

Concerning Newton's laws, I never know which is which, so please help me.
 
  • #3
Newton 2 law F = ma F = I* alpha
 
  • #4
I see. Should read
T = I[alpha].

Now you ask "are the forces ... Newton's second law".
Sorry for nit-picking a bit, but of course forces cannot 'be' a law.
Better to ask: "Does this law apply to a situation in which these forces act on a spinning object".

My answer is: "Yes, but."

Here's the 'but':
T and [alpha] are both vectors. So I must be a tensor (something representable by a matrix).
This means, physically, that a rotating body does not have >it's< moment of inertia I, but I is defined WRT an axis.

In general, a spinning top will not have a constant axis of rotation, but will show nutation and precession. Just think of a gyroscope.

OK, you could say "I do not care about nutation and stuff, I just assume the axis stays the same all the time".

In this case, |T| = I|[alpha]| (a scalar equation) is correct.
 

1. What is the difference between spin and torque in physics?

Spin and torque are two different concepts in physics. Spin refers to the intrinsic angular momentum of a particle or object, which is a property that is independent of its motion. Torque, on the other hand, refers to the rotational force applied to an object that causes it to rotate around an axis. In simpler terms, spin is a property of an object, while torque is a force acting on an object.

2. Can spin and torque be used interchangeably in physics?

No, spin and torque cannot be used interchangeably in physics. As mentioned before, spin is a property of an object, while torque is a force acting on an object. They have different units of measurement and represent different physical quantities.

3. How are spin and torque related to each other?

Spin and torque are related in the sense that torque can cause an object to spin or rotate around an axis. This is known as rotational motion, and the amount of rotation is determined by the torque applied. The spin of an object, however, is a property that is independent of its motion and is not directly affected by torque.

4. Can spin and torque be applied to all objects?

Yes, both spin and torque can be applied to all objects. Spin is a property that all objects possess, although the amount of spin may vary depending on the object. Torque, on the other hand, can be applied to any object that can rotate around an axis, such as a wheel or a spinning top.

5. How is spin different from angular momentum in physics?

Spin and angular momentum are different concepts in physics, although they are related. Spin is a type of angular momentum that is specific to particles or objects with intrinsic angular momentum. Angular momentum, on the other hand, can refer to the rotational motion of any object, whether it has intrinsic angular momentum or not.

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