Fill in the blank spaces. Many forces are known as "a)
forces" because they only act when things
touch. There are also some forces which
push or pull without touching. These are
called "b) forces". Examples
are c)
electrical force and
d)
..force.
Our modern understanding of forces
began
with
e)
(person) about 300 years ago.
He figured out how forces cause things to
f)and to stop moving. He
figured out that things fall down because of
the force of g)