Professor Dave again, I want to tell you
about Newton's second law.
We learned about Newton's first law of
motion, which tells us that an object
will continue its state of motion unless
acted upon by some net force. The second
law continues from there, describing what
will happen if some net force is indeed
present, whether from internal or
external forces. This law tells us that
force is equal to mass times
acceleration.
This is summarized in the following
equation, F = ma.
What it means is that we can do
quantitative calculations relating the
magnitude of a force applied to an
object, the mass of the object, and the
magnitude of the acceleration that
object will experience, and it shows the
derivation of the Newton as the SI unit
of force when we plug in 1 kilogram and
one meter per second squared for mass
and acceleration. There are a number of
things we can say about this equation,
which is tiny but powerful. First it
means that heavier objects will require
the application of greater force in
order to achieve the same acceleration
as lighter objects, with acceleration being
equal to force divided by mass. If we
want these objects of varying masses
each to accelerate at one meter per
second squared,
these are the magnitudes of the forces
that must be applied in order for the
math to work out. This also means that
the second law can be rephrased to state
that the acceleration an object
experiences will be directly
proportional to the force applied and
inversely proportional to its mass. It is
important to note that the net force is
the sum of all the forces acting on an
object. If multiple forces are acting on
an object, which is often the case, we
will need to represent them all in a
free body diagram and then add up all
the vectors to find the net force, which
will tell us
the direction of the acceleration that
will occur in response to the net force.
This kind of vector addition allows us
to make predictions about the motion of
an object even when it is being pushed
or pulled in a variety of ways. Since
forces are vectors they can be split up
into x and y components, which will be
useful for doing calculations in certain
scenarios that we will investigate later.
Newton's second law of motion has an
incredible range of applications, as it
can be applied to any force that exists
and it describes the motion of all
accelerating objects in the universe. We
can even use it to do things like
calculate the masses of faraway
celestial objects, but for right now we
will just stick to the basics, so let's check comprehension.
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