Download Newton`s Second Law

Newton’s
Second Law
TEKS 8.6A demonstrate and calculate how
unbalanced forces change the speed or
direction of an object’s motion
TEKS 8.6C investigate and describe
applications of Newton’s law of force and
acceleration
Net Force, Mass
and Acceleration
Isaac Newton discovered
one of the most important
laws of nature; the
relationship between
net force, mass (inertia)
and acceleration.
https://www.youtube.com/watch?v=M6iI5T3Yzbo
Newton’s Second Law
states that the net force
acting on a mass causes
the mass to accelerate in
the direction of the net
force.
A shorthand way of
writing this law is:
f = ma
f = force in newtons (N)
m= mass in kilograms (kg)
a = acceleration in meters per
second per second (m/s2)
Objects with
more mass are
more difficult
to accelerate.
If the same force
is applied to
two objects with
different masses,
the one with the
smaller mass will
accelerate more.
More mass
means less
acceleration,
unless a
larger force
is applied.
Same Forces
leads to
small mass
large acceleration
leads to
large mass
small acceleration
Different Forces
small force
small mass
can lead to
large force
large mass
Same Acceleration
Falling Objects and
Newton’s 2nd Law
The Italian
physicist
and
astronomer,
Galileo Galilei,
studied
falling objects.
He found that when
two objects of
different masses
are dropped, they
fall at the
same rate.
This was never fully
understood until Isaac
Newton announced his
Second Law of Motion.
In the case of free
falling objects,
the force is equal to
the weight of the object,
which is determined by
the acceleration
2
of gravity (9.8 m/s ).
Try dropping a book
and a ball of paper.
See what happens.
Now try dropping a piece
of paper and a book.
Most likely you will see
that the paper falls more
slowly.
Remember the book
has more weight than
the paper, so it has
more force to resist
friction from the air.
Try dropping the book with
the paper against the lower
surface of the book.
What happens?
Now try dropping the book with
the paper on top of the book.
How will the
accelerations of
the book and
the paper
compare?
Will they
separate
and fall
differently?
2 m/s2
m=50kg
f=
m=2000 kg
100N
f = 100N
How much force will be
required to move the
object in each picture?
.05 m/s2
What direction are the forces
applied in each picture?
2 m/s2
m=50kg
f = left
f= right
m=2000 kg
.05 m/s2
Will the rock and the van
accelerate at the same rate?
No, the rock will accelerate faster.
m=50kg
2 m/s2
f=
f =
m=2000 kg
.05 m/s2