He tuhinga mō te ture tuarua a Newton mō te nekehanga hurihuri
4.1 Te whanaungatanga i waenga i te au o te kaha, te au o te korekore, me te whakaterenga koki
Mena he kaha hua (ΣF) e pā ana ki tētahi mea he papatipu (m) tōna, ka neke te mea i runga i te rārangi me tētahi whakaterenga (a). Ko te whanaungatanga i waenga i te kaha hua, te papatipu, me te whakaterenga ka whakaaturia e te whārite:
Σ F = ma
Koinei te whārite o te ture tuarua a Newton .
Ko ngā rahinga o te nekehanga hurihuri e ōrite ana ki te kaha hua (ΣF) i roto i te nekehanga rārangi ko te iahiko hua o te kaha (Στ). Ko ngā rahinga o te nekehanga hurihuri e ōrite ana ki te papatipu (m) i roto i te nekehanga rārangi ko ngā iahiko o te korekore (I). Ko ngā rahinga o te nekehanga hurihuri e ōrite ana ki te whakaterenga (a) i roto i te nekehanga rārangi ko te whakaterenga koki (α).
Mena he pānga o te kaha (Στ) ki tētahi mea he kaha ā-pūmau tōna (I), ka huri te mea me tētahi whakaterenga koki (α). Ko te whanaungatanga i waenga i te kaha ā-pūmau, te kaha ā-pūmau, me te whakaterenga koki ka whakaaturia mā te whārite:
Στ = I α
He rite tēnei whārite hurihuri ki te ture tuarua a Newton.
4.2 Ngā tauira raruraru o te ture tuarua a Newton mō te nekehanga hurihuri
Tauira raruraru 1.
He porotaka totoka he taumaha 1 kg te taumaha, he 10 cm te whānui, kei ngā taha he taura kua takai, kei tetahi pito o te taura he kawenga 1 kg te taumaha. Whakaarohia he kore taumaha te taura. Whakatauhia te rahi o te whakaterenga o te kawenga ina taka noa ki raro. (g = 10 m/s2)
Rongoā:
Mōhiotia:
F = w = mg = (1 kg)(10 m/s 2 ) = 10 N
r = 0.1 mita
E hiahiatia ana: Te whakaterenga o te kawenga
Rongoā:
Tuatahi, tatauhia te au o te korehau me te au o te kaha.
Te wā o te korekore o te pūreirei totoka:
I = 1⁄2 mr 2 = 1⁄2 (1 kg)(0.1 m) 2
I = (0.5 kg)(0.01 m² ) = 0.005 kg m²
Te wā o te kaha:
τ = F l = (10 N)(0.1 m) = 1 N m
Whakaterenga koki:
Te whakaterenga o te kawenga:
a = r α = (0.1)(200) = 20 m/s 2
Tauira raruraru 2.
I te taha o te porotiti totoka he 2M te taumaha, ā, he R te whānui, i takai i tētahi taura, ko tētahi pito o te taura he kawenga he taumaha m. Ina tangohia te kawenga, ka huri te porotiti me te whakaterenga koki. Mena ka herea te porotiti ki tētahi mea he taumaha M, kia huri ai te porotiti me te whakaterenga koki ōrite, tātaihia te taumaha o te kawenga. (1 porotiti = 1⁄2 MR 2 ).
Rongoā:
Mōhiotia:
Taumaha o te pūraka totoka: 2M
Te pūtoro o te porotaka totoka: R
Papatipu o te kawenga: m
E hiahiatia ana: Te taumaha o te kawenga
Rongoā:
Tātaihia te wā o te korehau o te pūraka totoka, i mua atu, ā, i muri i te whakapiri i ngā mea he papatipu M:
Te wā o te korekore 1: I = 1⁄2 mr 2 = 1⁄2
(2M)(R) 2 = MR 2
Te wā o te korekore 2: I = 1⁄2 mr 2 = 1⁄2
(2M + M)(R) 2 = 1⁄2 (3M)(R) 2 = 1.5 MR 2
Te wā o te kaha e pā ana ki te pūwero e te kawenga:
τ = F l = (m)(g)(R)
He rite tonu te whakaterenga koki o te pūrakau, i mua atu, i muri hoki i te tāpiritanga o ngā mea he papatipu M tō rātou.
Papatipu o te kawenga = 1.5 ngā wā o te papatipu o te kawenga taketake.
