Kind: captions
Language: en
what are the forces acting on you right
now I want to answer this question by
introducing something called a free body
diagram this is a sketch that scientists
make that shows all the forces acting on
an object each force is represented by
an arrow the size of the arrow
represents the magnitude of the force
and its direction indicates the
direction of the force so for example
right now there is a Down W
gravitational force on me that pulls me
towards the center of the earth there's
another force that a lot of people don't
think about but is pretty important and
it's the force from the ground pushing
me
upward for most people it's kind of
strange to think that the ground which
is something inanimate could be putting
a force up on me but let me try to
convince you that the Earth really is
pushing up on me by uh stepping on this
toy here that supported by a
spring as I step onto the spring it
contracts so you can imagine the spring
must be trying to expand out and put a
force
outwards so that force in effect
supports me pushes up on my feet and
balances the gravitational force down so
that I remain
motionless now the ground is very
similar to this spring the ground is
just a very stiff spring but every time
you step you compress the ground a
little bit and that is enough to make
the ground create a force on you pushing
you back up and the force of the ground
upwards must be equal to the
gravitational force downwards so that
you stay at rest for Simplicity we draw
all forces acting through the center of
mass of an object so even though the
force is acting on my feet I can draw
that Force upwards as acting through
Myer Center of mass so there are really
only two main forces on you the force of
gravity downwards and something we call
the normal force which pushes you back
up the reason we call it the normal
force is because the word normal means
perpendicular and the force is
perpendicular to the surface that you're
standing
on