Download 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
Newton’s Second Law
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.
 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
large acceleration
small mass
leads to
small acceleration
large mass
Different Forces
small force
small mass
can lead to
large force
large mass
same acceleration
Falling Objects and Newton’s 2nd Law
 Galileo Galilei, the Italian physicist and astronomer, studied falling objects.
He found that when two objects of different masses are dropped, they fell 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 of gravity (9.8 m/s2).
 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?
How much force will be required to move the object in each picture? 100 N
What direction are the forces applied in each picture? left (rock), right (van)
Will the rock and the van accelerate at the same rate? No, the rock will
accelerate faster.
2 m/s2
m=50kg
f=100N
f = 100N
m=2000 kg
.05 m/s2
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
Newton’s Second Law
Net Force, Mass and Acceleration
 Isaac _______________ discovered one of the most important laws of
nature; the relationship between ______________, ____________
(inertia) and ___________________.
 Newton’s second law states that the net force acting on a mass causes the
_____________________________in the __________________ of the
net force.
 A shorthand way of writing this law is:
f = force in newtons (N)
___________
m= mass in kilograms (kg)
a = acceleration in meters per second per second (m/s2)
 Objects with _____________ mass are more difficult to
________________. If the __________ force is applied to two objects
with different masses, the one with the _______________ will accelerate
_____________. More mass means less acceleration, unless a
__________________ __________ is applied.
______ Forces
small mass
leads to
________acceleration
leads to
large mass
______ acceleration
________ Forces
small force
small mass
can lead to
large force
large mass
_______ acceleration
Falling Objects and Newton’s 2nd Law
 _______________, the Italian physicist and astronomer, studied falling
objects. He found that when two objects of ___________________ are
dropped, they fell at the ____________________. This was never fully
understood until Isaac Newton announced his second law of motion.
 In the case of free falling objects, the _______________ is equal to the
_____________ of the object, which is determined by the acceleration of
gravity (___________________).
 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 __________. Remember the book has more _________
than the paper, so it has more __________ 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? _____________________________________________________
_______________________________________________________________
How much force will be required to move the object in each picture? ________
What direction are the forces applied in each picture? _______ (rock), ____(van)
Will the rock and the van accelerate at the same rate? ___________________
__________________________________________________________
2 m/s2
m=50kg
f=100N
f = 100N
m=2000 kg
.05 m/s2