Answer: a scientific theory must be testable and capable of being proven false.
From this picture, we can learn many things.
One of them is: You have nice toes on your left foot.
#10). That's 'electric current'.
#11).
On the left: Only one possible path for current. That's a series circuit.
On the right: Two (or more) possible paths for current. That's a parallel circuit.
#12).
If lamp-A burns out, lamp-B will go out too. All of the current for both lamps has to flow through both of them, because that's the only path in the circuit. If one lamp burns a hole in itself, then current can't flow through the circuit any more, and everything goes out. That's how a series circuit behaves.
If lamp-C burns out, lamp-D continues to shine. Even though current can't flow through lamp-C any more, it can ctill flow through lamp-D, so lamp-D doesn't care. It keeps shining.
#13).
No, they don't have to. If there's ENOUGH charge built up on them,
then the attraction between the charges is strong enough to jump across
from one object to the other one.
This is exactly what happens when ENOUGH charge builds up on the
bottom of a cloud ... the charge can jump across the whole open space
between the cloud and the ground. We call that "lightning".
#14). I'm not sure I can explain this with things you've already learned.
Try this:
Electrons have to do some work to flow through a wire. That's why
we need a battery to make current flow in a circuit. The battery
supplies energy for the electrons to use on their trip through the wire.
The electrons give up some of their energy as they flow through the wire,
and it comes out of the wire in the form of heat energy.
(If there was ENOUGH current flowing through the wire, then the wire
would get so hot that it would glow. This is exactly what's going on in
a light bulb.)
#15).
Look back at the picture of the parallel circuit ... the one with lamps C and D.
Let's say the student built the circuit with only lamp-C in it, and then he
wanted to increase the current in the circuit. There are two ways he could
do that:
. . . . . Put in a battery with more voltage.
. . . . . Add the other lamp ... lamp-D. Now that the current has two
possible paths, more current will come out of the battery, and some
of it will follow each path.
#16).
I talked about this earlier.
The 'filament' is the little thin wire inside the light bulb. It's made to get
very hot and start to glow when current flows through it. It can do that
for a long time without burning up, because all the air has been pulled
out of the bulb. But sooner or later, that little skinny wire is going to break,
and then, there's no path for current to flow through the bulb. We call it
a "burned out" bulb.
#17).
If the resistance in the circuit changes (and the voltage of the battery
stays the same), then the current in the circuit decreases.
#18).
When you rub the balloon against your hair, electrons come off of
one surface and jump onto the other one ... I can never remember
whether the electrons jump to the balloon or to the hair. But whatever
direction it is, the balloon becomes charged ... either it has too many
electrons (negative charge) or else it has not enough electrons (positive
charge).
When you put the balloon up against the wall, some charges in the wall
move either toward or away from the balloon. THEN, you have two charged
objects, attracting each other, so they stick, until some charges leak away
onto air molecules that pass by.
#19).
Whenever we see electrical stuff going on, it's always electrons that are moving.
You've learned how an atom is built ... electrons in a cloud around the outside,
and the protons in the nucleus, deep deep deep deep inside the atom.
The nucleus is kind of protected from the outside world by being inside the
cloud of electrons. Nothing leaves the nucleus unless it's in a radioactive
substance, or else it's being shot with high-energy particles in an "atom
smasher" in a Physics laboratory. In the everyday world, it's only electrons
flowing through electrical things, jumping from clouds to the ground in lightning,
or jumping between your finger and the doorknob after you walk across the
carpet.
#20).
Again, this is an awful lot of work for 5 points, and you don't learn very much
when somebody else gives you whole answers. So I'm going to stop here,
and leave the rest to you or to another Brainly contributor.
The two different isotopes have weights :
w1 = 78.918 amu
w2 = 80.916 amu
average weight w3 = 79.903 amu
The mixing of two components can be modeled as
let the fraction of w1 be 'x'
hence 
now this is a linear equation in 'x'. Substituting the values we get
x = 0.507
hence the percentage of Br79 = 50.7% and the percentage of BR81 = 49.3%
Answer:
in 90 seconds It'll travel 450m At constant speed of 5m/s
