It is how much the x values can expand on a graph
This one is best done by elimination:
We need to start 4 meters away, so B is clearly wrong.
We first move towards Mr. Wilson (i.e. distance is decreasing) so A is wrong.
Our speed is faster on the way back, so the two sloped section must have differing slopes, so D is wrong.
(D also doesn't start at 4, it's wrong for two reasons.)
Only C is left.
We can check each part to make sure. First we start at 4m, then move away, then stay still (zero slope) for three seconds, then move back faster (higher slope). All parts check out ok.
1 electron has a mass of 9.1 X 10-31 kg. How many electrons n does it take to make 1 kg?
(1 e)/(9.1 X 10-31 kg) = n/(1 kg)
So, n = 1.10 X 1030 electrons
Each electron has a charge of 1.6 X 10-19 C, where C stands for Coulombs. So, the n electrons have a charge of q = ne = (1.10 X 1030 electrons) X (1.6 X 10-19 C/electron) = 1.76 X 1011 C.
An explicit equation is an equation used to find a term in a sequence without using the any previous terms. For example, if I have the set of numbers 1, 3, 5, 7, 9, my explicit equation is F(n)=2(n-1)+1. If I plug 1 in for n, I get F(1)= 2(0)+1, which is 1, my first term.
Hope this made sense.
