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# the following calculations all involve physical quantities Watch

1. (Original post by Zacken)
Fair enough.
In this two plusses and two minuses case you could be comparing the differences between two pairs of reactions ^.^
(a-b)-(c-d) if greater than 0 the difference between the first pair is larger etc
2. (Original post by ValerieKR)
In this two plusses and two minuses case you could be comparing the differences between two pairs of reactions ^.^
(a-b)-(c-d) if greater than 0 the difference between the first pair is larger etc
Haha, thanks! This is why I'll stick to maths, ygm
3. Also i have to convert 200 pF to standard form written to 1 decimal place, is the answer 2.0*10^-14?
4. (Original post by p29)
also i have to convert 200 pf to standard form written to 1 decimal place, is the answer 2.0*10^-14?
2.0*10^-10F
5. (Original post by ValerieKR)
2.0*10^-10F
thanks
6. This exercise is testing your understanding of physical quantities ("mass", "current") and their corresponding units ("kg", "A").

It makes sense to add 1 kg to 1 kg, or 1 A to 1 A, but makes no sense to add 1 kg to 1 A, because the result would not be a mass or a current.

The most important thing is that every physical quantity must have a unit. So every time you see a number without a unit, make an alarm bell go off in your head. 2.0*10^-14? 2.0*10^-14 whats? 2.0*10^-14 Farads, microFarads, apples, leprechauns? Without the unit, it's just a number with no obvious physical meaning.

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