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Newton’s Laws
Example ProblemA plane fires a bullet with an initial velocity of
150 m/s at an angle of 370 below the horizontal. The bullet lands 3 seconds later.
Find the components of the initial velocity. How far does the bullet travel in the
horizontal direction before it lands? How high above the (level) ground was the
plane when the bullet was fired? Find the magnitude of the velocity of the
bullet right before it hits the ground.
Pretest #3(“the crate in the snow”)
v
a
Pretest #3(“the crate in the snow”)
Fby gravity
Fby snow
Pretest #3(“the crate in the snow”)
Fby gravity
Fby snow
?
Motion(kinematics)
Forces(dynamics)
Causes
Types of Forces
Noncontact Forces Contact Forces
Pushes PullsElectromagnetic
Types of Forces
Noncontact Forces Contact Forces
Gravitational Pushes PullsElectromagnetic
Types of Forces
Noncontact Forces Contact Forces
Gravitational Pushes Pulls
W
Electromagnetic
Types of Forces
Noncontact Forces Contact Forces
Gravitational Pushes Pulls
Electric Magnetic
W
Electromagnetic
Types of Forces
Noncontact Forces Contact Forces
Gravitational Pushes Pulls
Electric Magnetic
W
M
Electromagnetic
Types of Forces
Noncontact Forces Contact Forces
Gravitational Nuclear Pushes Pulls
Electric Magnetic
W
M
Electromagnetic
Types of Forces
Noncontact Forces Contact Forces
Gravitational Nuclear Pushes Pulls
Electric Magnetic
Tension
W
M
Electromagnetic
Types of Forces
Noncontact Forces Contact Forces
Gravitational Nuclear Pushes Pulls
Electric Magnetic
Tension
W
M
T
Electromagnetic
Types of Forces
Noncontact Forces Contact Forces
Gravitational Nuclear Pushes Pulls
Electric Magnetic Normal
Tension
W
M
T
Electromagnetic
Types of Forces
Noncontact Forces Contact Forces
Gravitational Nuclear Pushes Pulls
Electric Magnetic Normal
Tension
W
M
T
N
Electromagnetic
Types of Forces
Noncontact Forces Contact Forces
Gravitational Nuclear Pushes Pulls
Electric Magnetic Normal
Tension
W
M
T
Nperpendicular to
surface
Electromagnetic
Types of Forces
Noncontact Forces Contact Forces
Gravitational Nuclear Pushes Pulls
Electric Magnetic Friction Normal
Tension
W
M
T
Nperpendicular to
surface
Electromagnetic
Types of Forces
Noncontact Forces Contact Forces
Gravitational Nuclear Pushes Pulls
Electric Magnetic Friction Normal
Tension
W
M
T
N fperpendicular to
surface
Electromagnetic
Aristotle384 - 322 B.C.
What is the velocity of this room?
RE = 6 x 106 m
v = 2 RE
t
= 400 m/s
Galileo Galilei (1564-1642)
Ball on Ramp
Ball on Ramp
Ball on Ramp
Ball on Ramp
Ball on Ramp
a=0
An object at rest stays at rest and an object in motion stays in motion at constant speed in a straight line, unless acted upon by a net force.
Sir IsaacNewton
(1642-1727)
Newton’s 1st Law: No net force - no acceleration
No acceleration = constant velocity
An object at rest stays at rest and an object in motion stays in motion at constant speed in a straight line, unless acted upon by a net force.
Newton’s 2nd Law: Deals with the effect of forces on
an object.
Motion of the Block
at rest
uniform motion to the right
moves to the right and speeds up without changing direction
moves to the right, slows down and stops without changing direction
Velocity Acceleration Push or Pull Necessary to Maintain Motion
Dry Ice on Slate
0 0 0
0 0
Motion of the Block
at rest
uniform motion to the right
moves to the right and speeds up without changing direction
moves to the right, slows down and stops without changing direction
Velocity Acceleration Push or Pull Necessary to Maintain Motion
Dry Ice on Slate
0 0 0
0 0
Newton’s 2nd Law: Net force causes acceleration (not velocity) The net force is the vector sum of all the individual
forces on an object.
WE,b
Nr,b
Nr,b
Fnet
WE,b
a
Acceleration is in same direction as the net force.
a
Types of Forces
Noncontact Forces Contact Forces
Gravitational Nuclear Pushes Pulls
Electric Magnetic Friction Normal
Tension
W
M
T
N f
Electromagnetic
Which one is the net force?
Pretest #3(“the crate in the snow”)
Fby gravity
Fby snow
?
Pretest #3(“the crate in the snow”)
Fby gravity
Fby snow
