Download Newton`s Second Law

Newton’s Second Law
of Motion—Force and
Acceleration
Chapter 5
Acceleration
Acceleration depends on the net force
acting on an object
Acceleration ~ Net Force
a is directly proportional to Fnet
 Acceleration depends on the mass of
the object
Acceleration ~ 1/Mass
a is inversely proportional to m

Acceleration
Newton’s Second Law
The acceleration produced by a net
force on an object is directly
proportional to the magnitude of the
net force, is in the same direction as
the net force, and is inversely
proportional to the mass of the object.
acceleration ~ net force/mass
a = F/m
Friction
Friction acts on materials that are in
contact with each other
 It depends on the types of material in
contact and how much of the surfaces
are pressed together
 Friction also occurs in liquids and
gases (fluid friction)
 Air Resistance – friction acting on
something moving through air

Air Resistance
Pressure
Pressure – the amount of force per
unit of area
Pressure = force/area applied
P = F/A
 Measured in Newtons per square
meter – called the Pascal (Pa)
 The smaller the area on which force is
applied, the greater the pressure

Pressure
Back to Free Fall

The acceleration of all objects in free
fall is the same, regardless of their
mass (the more massive an object,
the more force applied)
F/m
= F/m = g
Terminal Speed
When air resistance is present, a
falling object accelerates only until it
reaches its terminal speed
 At terminal speed, the force of air
resistance balances the force of
gravity
 The more massive an object, the
faster its terminal speed (it will take
longer for the forces to balance out)

Terminal Speed
Assignment (Due Monday, 10/13)
Read Chapter 5 (pg. 59-70)
 Do Ch. 5 Assessment #19-44 (pg. 7273)
 Do Appendix F, Ch. 5 #1-18 (pg. 666667)
