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urp:physrot
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urp:physrot [2021-11-08] nerf_herder |
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| τ = f*r (torque), (technically cross product r x f, or r x (m*α x r) | τ = f*r (torque), (technically cross product r x f, or r x (m*α x r) | ||
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| τ = I*α | τ = I*α | ||
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| τ (torque, Greek tau) = Ia (a = acceleration), units are Nm (Newton-meters) | τ (torque, Greek tau) = Ia (a = acceleration), units are Nm (Newton-meters) | ||
| + | |||
| τ = Iα is rotational equivalent to f = ma (many parallels to linear forces, etc) | τ = Iα is rotational equivalent to f = ma (many parallels to linear forces, etc) | ||
| + | |||
| Angular Momentum L = Iω | Angular Momentum L = Iω | ||
| If L₁ is angular momentum of ice skater with arms out: | If L₁ is angular momentum of ice skater with arms out: | ||
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| so Vpt = 2Vcm. Conversely, when in contact with the ground, Vrel = -Vcm, | so Vpt = 2Vcm. Conversely, when in contact with the ground, Vrel = -Vcm, | ||
| so vPt = 0. | so vPt = 0. | ||
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| - | |||
| - | ====Optics==== | ||
| - | Refraction on going into a different medium | ||
| - | |||
| - | **Snell's law** | ||
| - | sin(θ₁) / sin(θ₂) = v₁/v₂ = n₂/n1 (note that the n values are reversed) | ||
| - | v = velocity of light in that medium, n = index of refraction | ||
| - | v = c/n (c = speed of light in a vacuum) | ||
| - | it bends towards the normal direction when entering denser material | ||
| - | (and slows down). bend is because photons are waves. | ||
| - | |||
| - | Critical angle : smallest angle that results in total reflection, no refraction | ||
| - | θc = arcsin(n₂/n₁) | ||
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| ------- | ------- | ||
| Back to [[Physics]] page or [[00_start|Start]] page. | Back to [[Physics]] page or [[00_start|Start]] page. | ||
urp/physrot.txt · Last modified: 2021-11-08 by nerf_herder
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