bacontime

16 hours ago, Ethan_Sedai said:

because it is possible to Push and Pull from different points in your body,

I totally forgot about this, but their are WOBs that seem to confirm that this works. And this way has the advantage of not causing the target to spin widely.

The downside of course it that it causes the torque to be applied to the allomancer. So they'd need to anchor themself to something solid and burn pewter to handle the strain.

3 hours ago, Subvisual Haze said:

It's true the net force would result in zero net acceleration, but the energy of those forces just don't vanish though.

If the system is static, then no work is being done, and there's no actual energy transfer. Forces don't intrinsically have energy; they transfer energy when causing a displacement.

3 hours ago, Subvisual Haze said:

The allomancer here is being simultaneously pushed/pulled in 2 opposite directions at 6 g-force each.  OUCH!

Fortunately, the two forces applied to the allomancer both target the center of mass, so the net force on any particle of the allomancer is straight upwards, and they feel no torque. At least in theory. On the other hand, we know that allomancers can 'crush' themselves by flaring pushes in opposite directions simultaneously, so the forces aren't perfectly distributed throughout the body.

We don't know exactly how the forces are distributed, but given that the two force vectors here have only a small angle between them, I wouldn't expect it to cause severe problems. An experiment worth trying in-universe: Push and pull on the same object at the same time. Whether and where you feel bodily pressure would tell about how the forces are applied.

The building on the other hand does experience extreme torque, which is counteracted by the ground if the anchor points are stable enough.

As for the concern about pushing only part of an object: We see both Kelsier and Wax do this in canon. Also:

Quote

Kyrroti

If I were burning iron, where would the line point to on a steel hula-hoop?

Brandon Sanderson

For something like that, it would depend on the Steelpusher's power. For some, it would just be pointing generally toward the center of the hoop--but for skilled Steelpushers, they'd be able to see softer lines pointing in all directions around the hoop.

Skyward Pre-Release AMA (Oct. 12, 2018)

On 4/15/2019 at 5:14 PM, SwordNimiForPresident said:

They would need F-zinc or F-steel in order to change their push/pull location that fast, IMO. I'm not gonna attempt the math, but that thing would probably be spinning 10k+ RPM.

Say the radius of the idol is 10cm. (That's actually a bit too large for 25kg of brass, but eh, round numbers.) The moment of inertia of a solid ball is (2/5)*m*r^2, which works out here to 0.1 kg m^2.

The depicted forces apply 600 Nm/rad of torque.

So the  angular acceleration is 6000 radians per second per second. (Or ~57000 RPM per second)

In other words, it would take less than a second  for the surface of the ball to accelerate past the speed of sound. Hover juggling heavy objects is probably not possible without holding the bands of mourning.