# Rotational motion

#### SDTK

1. Homework Statement

this is a question just to help with my understanding: ....

when Torque (kg m^2/s^2) and the Moment of Inertia (kg m^2) are known and used to find angular acceleration, .... T(net)/I, are the units for the resulting acceleration rad/s^2

Thanks :-)

2. Homework Equations
$\tau = I \alpha$

3. The Attempt at a Solution
Example:
t = 12 kg m^2/s^2
I = 3.00 kg m^2

angular acceleration = torque/I = 12 kg m^2/s^2 / 3.00 kg m^2 = 4 units(?) / s^2

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#### gneill

Mentor
Yes. Angular acceleration is given in radians per second squared $(rad/s^2)$.

The radian is sort of a "unitless unit" that appears and disappears as required when working with angular quantities. It's based on a ratio of lengths from the unit circle, where an angle is defined via the arclength along the circle divided by the radius length. It serves to distinguish a quantity as being angular in nature.

• SDTK

thank you! :-)

#### haruspex

Science Advisor
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• SDTK

#### gneill

Mentor
How about "dimensionless unit"?
Sure! That's probably better nomenclature. • SDTK

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