Transcript Newton*s Laws of Motion

Newton’s 1st Law

Definition:
 An object at rest remains
at rest and an object in
motion maintains its position
unless it experiences an
Outside force.
Newton’s 1st Law

 Inertia is the tendency of an object at rest to remain at
rest or, if moving, to continue moving with a constant
velocity.
 All objects have inertia because they resist changes in
motion.
 The greater the mass
of the object the more
force required to
change it’s motion.
Concept Check 1

 Why should infants be placed in special-backward
facing car seats?
nd
2
Newton

Law
 Definition: The unbalanced force acting on an object equals the
object’s mass times its acceleration.
 Mathematically represented by the equation:
Force= mass x acceleration or F=ma
Cenzo was here
Remember the SI unit for force is a Newton
Newton= 1 kg x m/s2 towards center of the earth
Free Fall

 Definition: the motion of a body when only the force of
gravity is acting on it
 Acceleration near the Earth’s surface is constant.
 All objects on Earth accelerate at exactly 9.8
m/sec/sec.
 Gravity is abbreviated as g
Concept Check 2

 In the absence of air resistance which will hit the
ground first?
Weight

 Definition: The force on an object due to gravity is
called its weight
1 Newton= 1 kg x m/s2 towards center of the
earth= 0.22481 lbs or pounds
Apparent
Weightlessness

 Astronauts and their surroundings all accelerate at
the same rate. Consequently, the floor of the shuttle
pushes up against the
astronauts or objects
in the shuttle.

Terminal
Velocity
 Definition: the terminal velocity reached by a falling object
whose acceleration is zero. The terminal velocity of a falling
body occurs during free fall when a falling body
experiences zero acceleration. This is because of the
retarding force known as air resistance. Air resistance
exists because air molecules collide into a falling body
creating an upward force opposite gravity. This upward
force will eventually balance the falling body's weight. It
will continue to fall at constant velocity known as the
terminal velocity.
 http://hypertextbook.com/facts/JianHuang.shtml
Newton’s Second Law Math
Problems

 1. What is the net force necessary for a 3.6 x 103 kg
truck to accelerate forward at 2.0 m/s2.
 2. A baseball accelerates downward at 9.8 m/s2. If
the gravitational force acting on the baseball is 1.8 N,
what is the baseball’s mass?
 3. A bobsled and crew have a combined mass of 525
kg. If the bobsled experiences an unbalanced force of
1095 N pushing it forward, what is the bobsled’s
acceleration?
Newton’s

rd
3
Law
 For every action force, there is an equal and opposite
reaction force.
 Applies force always acts in pairs _.
 Principle used in rocketry.
End Check- complete on
a separate sheet

 1. Why won’t the elephant move?
 2. What is the difference
between weight and mass?
 3. If the elephant has a mass of
2000 Kg and the person is pushing
at 60 N what is the acceleration
of the elephant?
End Check- complete on
a separate sheet

 4. State each of Newton’s three laws of motion in your
own words and give an example that demonstrate each
law
 5. Explain the difference between mass and weight. Does
the weight of an object ever change? If so, when?
 6. Using Newton’s laws, predict what will happen when a
car traveling on a icy road
a. Comes to a sharp bend
b. Has to stop quickly
 7. How much does a 7.0 kg puppy weigh on Earth?