Te kaha noa ko te kaha e pā ana ki ngā mea e pā ana, ko te ahunga o te kaha he poutū ki te papa pa. Ko tōna tohu ko N, ā, pūnaha waeine ā-ao ko kg m/s2 Newton rānei.
Ākihia a N ki runga i te mata papatahi
Ko N te kaha e pā ana ki te papa i runga i te kurupae, ko N' te kaha e pā ana ki te kurupae i runga i te papa. Ko w te kaha ā-papa e pā ana ki te poraka, ki te taumaha rānei o te poraka. Ko N me N' ngā tauhohenga mahi, ko N ia me w ehara. te kaha tauhohenga mahi.
Mena kei te okioki te poraka, kāore rānei e neke poutū, ka taea te tatau i te rahi o te kaha N mā te whakamahi i te ture tuatahi a Newton.
ΣFy = 0
N – w = 0
N = w
Ki te pēhia te poraka ki raro me te kaha F pērā i te pikitia i te taha, ko te rahi o te kaha N ko:
ΣFy = 0
N – w – F = 0
N = w + F
Te kaha noa i runga i te papa whakarara
Ko N me N' ngā kaha mahi-tauhohenga. Ko N te kaha noa e pā ana ki te poraka, ā, ko N' te kaha noa e pā ana ki te papa whakarara. Ko W te wāhanga poutū o te kaha taumaha (w). Ka pā te kaha taumaha (w) ki te poraka. Ko te rahi o te kaha noa ko
ΣFy = 0
N – wy = 0
N = wy = w cos theta
