A father of massmfand his daughter of massmdsit on opposite ends of a seesaw at equal distances from the pivot at the center. The seesaw is modeled as a rigid rod of massMand lengthscript land is pivoted without friction. At a given moment, the combination rotates in a vertical plane with an angular speed?.
(A) Find an expression for the magnitude of the system s angular momentum.
(B) Find an expression for the magnitude of the angular acceleration of the system when the seesaw makes an angle?with the horizontal.
Physics question?
2016-03-22 3:58 pm
回答 (1)
2016-03-23 2:13 pm
(A) L = Σ I*ω
seesaw: Is = Mℓ² / 12
father: If = mf*(ℓ/2)²
daughter: Id = md*(ℓ/2)²
so
L = [M + 3(md + mf)]ℓ² * ω / 12
which can be expressed other ways depending on how you handle the denominators
(B) Assuming md < mf, then
(mf - md) * g * ℓ/2 * cosΘ = I * α = α * [M + 3(md + mf)]ℓ² / 12
so
α = 6(mf - md)gcosΘ / [M + 3(md + mf)]ℓ
which, again, might be expressed other ways.
Hope this helps!
seesaw: Is = Mℓ² / 12
father: If = mf*(ℓ/2)²
daughter: Id = md*(ℓ/2)²
so
L = [M + 3(md + mf)]ℓ² * ω / 12
which can be expressed other ways depending on how you handle the denominators
(B) Assuming md < mf, then
(mf - md) * g * ℓ/2 * cosΘ = I * α = α * [M + 3(md + mf)]ℓ² / 12
so
α = 6(mf - md)gcosΘ / [M + 3(md + mf)]ℓ
which, again, might be expressed other ways.
Hope this helps!
收錄日期: 2021-04-21 17:30:55
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20160322075848AAOj5vY