5 Ngā tauira o ngā pātai mō te pōrewarewa
1. Ko te taumaha o te kawenga i te hau he 3 N, ko te taumaha o te kawenga i te wai he 2,8 N. E hia te kaha pōrewarewa e pā ana ki te kawenga e te wai?
Kōrero:
2. 100 N te taumaha o te konganuku ina inehia i te hau, ā, 80 N ina inehia i te wai. He aha te rōrahi o te konganuku?
Kōrero:
E mōhiotia ana:
w = 100 N
hau w = 80 N
I pātaihia: Te rōrahi whakarewa ?
He ōrite te rōrahi o te konganuku e rumakina ana ki te wai ki te rōrahi o te wai kua nekehia.
3. Ko te taumaha o te toka he 10 kg. Ina paunatia ki te wai, ko te taumaha o te toka he 8,2 kg. He aha te matotoru o te toka?
Kōrero:
E mōhiotia ana:
karamu = 9,8 m/s2
m = 10 kg
m wai = 8,2 kg
I pātaihia: Te matotoru o te toka ( ?
Whakautu:
4. He poraka rakau he 2,5 m te roa, he 0,5 m te whānui, ā, he 0,4 m te matotoru. Mēnā ka rumakina te rakau ki te wai, ā, ko te mātotoru o te wai he 1000 kg/m3 , ko te kaha o te pēhanga ki runga ko … (g = 10 N/kg)
A. 400 N
B. 500 N
C. 4.000 N
D. 5.000 N
Kōrero
E mōhiotia ana:
Te rōrahi o te porowhita (V) = te roa x te whānui x te matotoru = 2,5 x 0,5 x 0,4 = 0,5 m3
Te mātotoru o te wai ( ρ ) = 1000 kg/m 3
Te whakaterenga nā te kaha ā-papa (g) = 10 N/kg
I pātaihia: Te rahi o te kaha pōrewarewa
Whakautu:
Te tātai kaha pūangi:
F = ρ g V
Whakaahuatanga: F = te kaha pōuri, ρ = Te mātotoru, g = te whakaterenga ā-papa, V = te rōrahi
Ko ngā rōrahi katoa o ngā mea kua totohu ki raro i te wai, nō reira ka tatauhia te kaha pōrewarewa mā te whakamahi i te tātai i runga ake nei.
F = (1000)(10)(0,5) = (1000)(5) = 5000 Ngā Niutona
Ko te whakautu tika ko D.
5. Ko te taumaha o te mea i te hau he 100 N, kātahi ka whakanohoia ki roto i te wai kia piki ake te rōrahi mā te 1,5 m3 . Mena ko te taumaha motuhake o te wai he 10 N/m3 , ko te taumaha o te mea i roto i te wai ko...
A. 1.500 N
B. 115 N
C. 85 N
D. 6,7 N
Kōrero
E mōhiotia ana:
Taumaha o te mea i te hau (w) = 100 Newton
Te pikinga o te rōrahi wai = te rōrahi o te mea e rumakina ana ki te wai (V) = 1,5 m3
Te taumaha motuhake o te wai = 10 N/m 3
E hiahiatia ana: Taumaha o tētahi mea i roto i tētahi wai
Whakautu:
Ko te tātai mō te taumaha o tētahi mea i roto i tētahi wai:
Taumaha o te mea i roto i te wai = taumaha o te mea i roto i te hau – te rahi o te kaha pōrewarewa
Taumaha o te mea i roto i te wai = 100 Newtons – te rahi o te kaha pōrewarewa
Tuatahi, tatauhia te rahi o te kaha pōrewarewa kia taea ai e koe te tatau i te taumaha o te mea i roto i te wai.
Te tātai kaha pūangi:
F A = ρ g V
Ngā Mōhiohio:
F A = te kaha pōrewarewa = te kaha e pā ana ki tētahi mea kei roto i te wai
ρ = te mātotoru o te wai
g = te whakaterenga nā te kaha ā-papa
V = te rōrahi o te mea e rumakina ana ki te wai
E mōhiotia ana te whakaterenga nā te kaha ā-papa (g), e mōhiotia ana te rōrahi o te mea e rumakina ana ki roto i te wai, engari kāore anō kia mōhiotia te mātotorutanga. Nō reira, tuatahi tatauhia te mātotorutanga o te wai.
Te taumaha motuhake:
Te taumaha motuhake o te wai = 10 N/m 3
w / V = 10 N/m 3
mg / V = 10 N/ m3
m (10) / V = 10 N/m 3
m / V = 1 kg/ m3
ρ = 1 kg/ m3
Nō reira, ko te mātotoru o te wai he 1 kg/ m3
Te kaha o te pūangi :
F A = ρ g V = ( 1 kg/m³ ) (10 m/s² ) (1,5 m³ ) = 15 kg m/s² = 15 Newton
Taumaha o tētahi mea i roto i tētahi wai:
Taumaha o te mea i roto i te wai = 100 Newton – 15 Newton
Taumaha o te mea i roto i te wai = 85 Newtons
Ko te whakautu tika ko C.
Ngā tauira pātai mō te ture a Archimedes
