Transcript Newton's Second Law of Motion

Newton’s Second Law of Motion
Bell Work
• Identify three forces acting
on a speeding bullet.
• Why do cars sometimes skid
going around corners on icy
roads?
Objectives
• Define and apply Newton’s
second law of motion to real
life situations.
• Relate the acceleration of an
object to the mass of the object
and the force applied to the
object.
Newton’s Second Law of Motion
• This law states that an
unbalanced force on an
object causes the object to
accelerate in the direction of
the force.
Force of wind
These forces are
unbalanced so the
boat accelerates in
the direction of the
unbalanced force.
Air/Water Resistance
20-30 mph
Gravity
Unbalanced
Forces
Table
If gravity becomes greater than the
upward force of the table, the papers
will accelerate downward.
Wagon moves
this way
Unbalanced
Force Applied
Force, Acceleration, and Mass
• The greater the force applied
to a given object, the greater
its acceleration.
Force, Acceleration, and Mass
• For a given force, the greater
the mass of an object, the
smaller its acceleration and
vice-versa.
Newton’s Second Law in Real
Life
• Why would a truck take longer to
accelerate when the driver hits the
gas if it were loaded with bricks than
if it were empty?
• How might you design a car to
achieve maximum acceleration?
Newton’s Second Law in Real
Life
• Using Newton’s second law
of motion, explain why
larger trucks usually need
more distance to stop than do
smaller trucks.
Science, Technology, & Sports
• Friction is the main force that
slows the speed of athletes in
sports such has skiing, swimming,
cycling, speed skating, and
running. How can these athletes
combat the effects of friction?
Formula for Newton’s Second
Law of Motion
• Newton’s second law of
motion can be expressed by
the formula F = ma.
• F stands for force, m stands
for mass, and a stands for
acceleration.
Formula for Newton’s Second
Law of Motion
• According to this formula, if
the force is constant and the
mass increases, what will
happen to acceleration?
Question
• Identical twins are riding in
identical wagons. A friend
gives the first wagon a
stronger push than the
second. Which twin will
experience greater
acceleration?
Question
• Would a car towing a boat take
less, the same, or more time to
accelerate than it would without
the boat? Explain.
Question
• What will happen to the
acceleration of an object if the
mass decreases and the force is
constant?
Question
• If two identical objects
accelerate at the same rate, what
must be true of the force
applied to each object?
Review
• Use Newton’s second law of
motion to explain why a freefalling object accelerates.
• How is the acceleration of an
object affected by the force
applied to it?
Challenge
• Using the formula a = f/m,
explain why all objects in
free fall have the same
acceleration, regardless of
mass.