Imagine having to keep anything that uses batteries
plugged into the wall for it to work. Cords would be stretched out all
over your home. Batteries allow us to make things like a television
remote mobile. We can pick them up and move around without tripping over
cords. How do batteries make this possible?
Batteries are a small container full of special
chemicals that make electricity. Batteries have a positive end and a
negative end. A barrier in the middle separates these ends from each
other. When the chemicals inside react, they make a tiny particle called
an electron. The electrons have a negative charge and collect together
at the negative end of the battery. The electrons get rather crowded at
the negative end and need to move to the empty positive end. To do this,
a wire must be connected to each end, like when you put the battery in
the TV remote. The electrons move through the wire and around the
barrier. Think of a football running back running around the defensive
end rather than bouncing off him and falling down. When the electrons
move to the positive end, they flow like a river through the wire. This
flow is electricity and it powers the devices we use. And that’s how
How does a boat float?
A boat made of steel floats on water, but a block
of steel sinks in water. How does the boat float instead of sinking to
In ancient Greece, a scientist by the name of
Archimedes (Ark-eh-meed-eez) came up with the principle, creatively
called the Archimedes Principle, which explains how a boat floats.
If you fill a bathtub and sit in it, the water in
the tub rises. This is because you displaced, or moved, the water, and
it had to go somewhere. The amount of water you displaced weighs the
same as the weight you put in the water. The same is true for a boat in
If a boat weighs 1,500 pounds, it will displace
1,500 pounds of water. So long as the boat displaces 1,500 pounds of
water before the boat is submerged, the boat floats.
So how does the water “know” when 1,500 pounds has
been moved out of the way? Floating actually has more to do with the
amount of pressure rather than weight. The boat puts pressure on the
water, and the water puts pressure on the boat. The upward pressure
pushing on the bottom of the boat is what causes it to float. Each
square inch of the boat that is underwater has water pressure pushing it
upward, and this combined pressure causes the boat to float.