Nā ʻatikala e pili ana i ke ʻano wehewehe a me nā ʻano o nā nalu mechanical
KA WEHEWEHE ʻANA O NĀ NALU MEKANIKA
Inā ʻoe e paʻa i kekahi wēlau o ke kaula a hoʻoluliluli iā ia i luna a i lalo, e ʻike ʻia kahi nalu e pālahalaha ana ma ke kaula. A i ʻole inā ʻoe e hoʻokuʻu i kahi pōhaku i loko o ka wai, e ʻike ʻia nā nalu ma luna o ka wai. ʻO ke kaula a me ka wai e hoʻoluliluli wale i luna a i lalo, ʻaʻole e neʻe pālahalaha. ʻO nā nalu ma ke kaula a me nā nalu i loko o ka wai he mau laʻana o nā nalu mechanical.
ʻO nā nalu mīkini he mau nalu e holo ana ma o kahi waena. ʻO nā hiʻohiʻona o nā nalu mīkini he mau nalu ma nā kaula a i ʻole nā kaula, nā nalu i loko o ka wai, nā nalu kani e pālahalaha ana i loko o ka lewa, a me nā nalu ōlaʻi e pālahalaha ana i loko o ka lepo. Hiki i nā nalu ke hele i nā wahi lōʻihi ʻoiai ke waena e haʻalulu ai nā nalu a puni ke kiko kaulike.
Nā ʻAno o nā Nalu Mekanika
Ma muli o ko lākou ʻano, ʻelua ʻano nā nalu mechanical, ʻo ia hoʻi nā nalu transverse, a me nā nalu longitudinal.
ʻO nā nalu transverse he mau nalu e kū mai ana ke kū pololei ke kuhikuhi o ka neʻe ʻana o ka nalu i ke kuhikuhi o ka neʻe ʻana o ka ʻāpana. No ka laʻana, nā nalu ma ke kaula, nā nalu ma ka wai.
Inā neʻe nā nalu o ke kaula i ke kuhikuhi ʻākea, neʻe nā ʻāpana o ke kaula i ke kuhikuhi kū. Pēlā nō, inā neʻe nā nalu wai i ke kuhikuhi ʻākea, neʻe nā ʻāpana wai i ke kuhikuhi kū.
ʻO nā nalu longitudinal nā nalu e kū mai ana i ka wā e kūlike ai ke kuhikuhi o ka neʻe ʻana o ka nalu me ke kuhikuhi o ka neʻe ʻana o nā ʻāpana. Eia kekahi laʻana, nā nalu i loko o nā pūnāwai, a me nā nalu kani i ka lewa.
Inā neʻe ka nalu ma ka pūnāwai i kahi ʻaoʻao pae, a laila neʻe pū ka nui a me ke kaumaha i hana ʻia i loko o ka pūnāwai i mua a i mua i ke ʻaoʻao pae.
Pēlā nō, inā neʻe ka nalu kani i ke kuhikuhi kū pololei, ʻuʻuku ka ea a kīkoʻo i ke kuhikuhi kū pololei.
ʻO nā nalu ʻōlaʻi he mau nalu transverse (i kapa ʻia he mau nalu shear) a me nā nalu longitudinal (i kapa ʻia he mau nalu pressure).
HŌʻULUʻULU NALU MĀKANIKA
Haʻilula Nalu Transverse
Hoʻohana ʻia kekahi mau nui e wehewehe i nā nalu, ʻo ia hoʻi ʻo Amplitude (A), Frequency (f), Period (T), a me ka Speed Nalu (v).
ʻO ka amplitude ka ʻokoʻa kiʻekiʻe loa. ʻO ka wā ka manawa o ʻelua mau piko/awāwa nalu e hele ana ma kahi like ma ka lewa. ʻO ka alapine (frequency) ka helu o nā piko/awāwa e hala ana ma kahi like no kēlā me kēia anakahi manawa.
Neʻe nā nalu mechanical i kahi wikiwiki. ʻO ke ʻano hana o ka wikiwiki o ka nalu:
v = λ f = λ/T
v = ka wikiwiki o ka nalu, λ = ka nalu, f = ka alapine (frequency), T = ka wā.
ʻO ke anakahi honua no ka nalu he mika, ʻo ke anakahi no ke alapine (frequency) ʻo Hertz, a ʻo ke anakahi no ka wā he Sekona. ʻO ke anakahi no ka wikiwiki o ka nalu he mika/kekona.
Pilikia Laʻana:
He alapine (frequency) ko kahi nalu transverse ma ke kaula he 2 Hz (hele nā piko nalu ʻelua ma kahi like ma ka lewa, no 1 kekona) a he 3 mika ka lōʻihi o ka nalu (ʻo ka mamao ma waena o nā piko kokoke ʻelua he 2 mika). He aha ka wikiwiki o ka nalu?
ʻIke ʻia:
Alapine (f) = 2 Hz
Ka lōʻihi o ka nalu (λ) = 3 mika
Makemake ʻia: Wikiwiki (v)
pāʻoihana:
v = λ f = 3 (2) = 6 m/s
ʻO ka wikiwiki o kahi nalu transverse i loko o kahi medium e pili ana i ke ʻano o ka medium e hele ai. No ka laʻana, ʻo ka wikiwiki o ka nalu ma ke kaula (kaula, kaula, uea) e pili ana i ke kaomi ʻana i loko o ke kaula (FT) a me ka nui o ke kaula (ka nui o ke kaula no kēlā me kēia lōʻihi).
Pilikia Laʻana:
He 1 mika ka lōʻihi o kahi nalu a pālahalaha ma luna o ke kaula he 100 mika ka lōʻihi a he 2 kg ke kaumaha. ʻO ke kaomi ma ke kaula he 200 N. He aha ka wikiwiki o nā nalu i loko o ke kaula?
ʻIke ʻia:
Ka lōʻihi o ka nalu (λ) = 1 mika
ʻO ka lōʻihi o ke kaula (L) = 100 mika
ʻO ke kaumaha o ke kaula (m) = 2 kg
ʻO ke kaomi ma ke kaula (T) = 200 N
Makemake ʻia: Ka wikiwiki o nā nalu ma ke kaula (v)
pāʻoihana:
Ke ʻano o ka nalu longitudinal
ʻO ka wikiwiki o nā nalu lōʻihi i loko o kahi waena e pili ana i ke ʻano o ka waena e hele ai. Ua helu ʻia ka wikiwiki o nā nalu lōʻihi e pālahalaha ana ma nā koʻokoʻo paʻa me ka hoʻohana ʻana i ke ʻano:
v = ka wikiwiki o ka nalu, E = ka modulus elastic o Young, ρ = ka nui
Pilikia Laʻana:
E helu i ka wikiwiki o ka nalu kani e holo ana ma ke alahao kila. ʻO ka modulus elasticity o Young Steel = 2 x 10 11 N/m 2 a ʻo ka density o ke kila = 7.8 x 10 3 kg/m 3
ʻIke ʻia:
ʻO ka modulus elastic o ke kila (E) = 2 x 1011 N/ m2
Ka nui o ke kila (ρ) = 7.8 x 103 kg / m3
Makemake ʻia: Ka wikiwiki o nā nalu kani
pāʻoihana:
Ua helu ʻia ka wikiwiki o nā nalu longitudinal e pālahalaha ana i loko o nā wai a me nā kinoea me ka hoʻohana ʻana i ke ʻano hana: v = ka wikiwiki o ka nalu, B = modulus bulk, ρ = density
Pilikia Laʻana:
He aha ka wikiwiki o nā nalu longitudinal ke hele lākou i loko o ka wai?
Modulus o ka wai nui (B) = 2 x 109 N / m2
ʻO ka nui o ka wai (ρ) = 1000 kg/ m3
pāʻoihana:
Ka wikiwiki o ka nalu longitudinal i ka wā e pālahalaha ana i ka wai:
