2 Ngā tauira o ngā pātai mana
Ko te mana te tere o te mahi pakihi ngā mahi rānei i mahia i roto i tētahi wā kua whakaritea.
I roto i te tikanga ā-ira, ko te mana te ōwehenga o te kaha ki te wā.
P = W / t
Whakaahuatanga: P = mana (wae Joule/hēkona), W = mahi (Joule) me t = wā (hēkona)
I runga i tēnei whārite, ka taea te whakatau ko te nui ake o te tere o te mahi, ko te nui ake o te mana, engari, ko te iti ake o te tere o te mahi, ko te iti ake o te mana.
He rahinga tauine te mana. Ko te pūnaha ā-ao mō ngā waeine mana ko te joule/hēkona. Ko te joule/hēkona = watt (whakarāpopototanga W), i tapaina hei whakahonore i a James Watt.
Ko te pūnaha mana o Peretānia he 1 pauna-wae-kaha ia hekona. He iti rawa tēnei waeine mō ngā mahi whaihua, nō reira ka whakamahia he waeine nui ake, ko te hōpaika (hp poto). 1 hōpaika = 550 pauna-wae-kaha ia hekona = 764 wati = ¾ kirowati.
Ka taea hoki te whakaatu i te nui o te mahi i roto i ngā waeine o te mana x te wā, hei tauira, te kilowatt-haora, te KWH rānei (Kilo Watt Hour). Ko te kotahi KWH te mahi i mahia i te tere pumau o te 1 kiro Watt mō te 1 hāora.
1. E piki ana tētahi tangata e 50 kg te taumaha i tētahi arawhata 10 mita te teitei mō ngā meneti e 2. Mena ko te whakaterenga nā te kaha ā-papa (g) he 10 m/s2 , ko te mana ka puta ko….
Kōrero
E mōhiotia ana :
Taumaha (m) = 50 kg
Teitei (h) = 10 mita
Te whakaterenga nā te kaha ā-papa (g) = 10 m/s2
Wā wā (t) = 2 meneti = 2 (60) = 120 hēkona
I pātaihia : mana (P)
Whakautu :
Tātai mana :
P = W / t
Whakaahuatanga: P = mana, W = mahi, t = wā
Tātai pakihi :
W = F s = wh = mgh
Whakaahuatanga: W = mahi, F = kaha, w = kaha ā-papatipu, s = nekehanga, h = teitei, m = papatipu, g = whakaterenga nā te kaha ā-papatipu.
I te piki arawhata, ka mahi te kaha o te papatipu ki te tangata. Ko te mahi e mahia ana e te kaha pūmau pērā i te papatipu ka whakawhirinaki ki te huringa teitei anake. Mā te mahi e mahia ana e te kaha o te papatipu ka piki ake te kaha pūmanawa papatipu o te tangata. Ko te mahi e mahia ana e te kaha o te papatipu ki te tangata ko:
W = mgh = (50)(10)(10) = 5000 Joule.
Nā reira, ko te mana e puta mai ana i te pikinga o te tangata i ngā arawhata ko:
P = W / t = 5000 / 120 = 41,7 Joule/hēkona.
2. Ka piki tētahi tangata he 60 kg te taumaha i tētahi rākau kokonati ki te teitei o te 5 mita i roto i te 10 hēkona. Ko te kaha e hiahiatia ana hei piki i te rākau kokonati ko… karamu = 10 m/s2
Kōrero
E mōhiotia ana :
Taumaha (m) = 60 kg
Teitei (h) = 5 mita
Te whakaterenga nā te kaha ā-papa (g) = 10 m/s2
Wā wā (t) = 10 hēkona
I pātaihia Mana
Whakautu :
Pakihi:
W = mgh = (60)(10)(5) = 3000 Joule
Mana:
P = W / t = 3000 / 10 = 300 Joule/hēkona.
