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:hippie: One very good one which isn't taught at schools but is often used chemistry lab is : pH + pOH = 14. so if yu need to know the pH of say 10mM NaOH, the pOH is neg log 1 x 10ex-2 = 2, so the pH must be 12. Good luck out there in the HSC.

Ratcher your maths is ok except the last formula of yours which sez r = 5.98 x 10^24 - 6.38 x 10^6. You put the wrong figures in, yu put the earth's mass rather than distance. should have been r (from Earth's surface) = your figure of 6.38 x 10^7 - 6.38 x 10^6 = 5.74 x 10^7 m from the...

As Jase says, resistance is a property of the wire that we assume doesn't change in these questions (although in reality, R increases as the temperature increases with power loss from the current). For transmission type questions, use P = VI to calculate current such as transmittng 64MW at...

my son (whose site this is) has shown me your question. I am a tutor with my own tuition centre in Sydney (Miranda), as well I tutor at James An Coaching. I mostly tutor physics and chemistry. I do maths also but not 3U as revision takes me too long. Anyway simple questions, ask away...