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Acceleration is the rate of change of velocity.
Acceleration is a vector
Motion at Constant Acceleration
v = v0 +at
1 2
d = v0 t+ at
2
Falling Objects
Near the surface of the
Earth,
due to gravity,
all objects experience
the same constant
acceleration
Falling Objects
In the absence of air
resistance, all objects
fall with the same
acceleration
g = 9.80 m/s2.
Newton’s First Law of Motion
Newton’s first law (inertia)
Every object continues in its state of rest, or of
uniform velocity in a straight line, as long as no
net force acts on it.
Newton’s Second Law of Motion
Newton’s second law
• acceleration and force
• acceleration is
• proportional to net force
• inversely proportional
to mass.
a  Fnet / m
Newton’s Third Law of Motion
Newton’s third law:
When one object exerts a force on a second
object,
the second exerts an equal force in the opposite
direction on the first.
Weight – the Force of Gravity
Weight is not mass
Weight is the force exerted on an
object by gravity.
Close to the surface of the Earth,
where the gravitational force is
nearly constant, the weight is:
Normal Force
An object at rest must have no net force on it. If
it is sitting on a table, the force of gravity is still
there; what other force is there?
The force exerted perpendicular to a surface is
called the normal force. It is
exactly as large as needed
to balance the force from
the object
Newtonian Gravitation
gravitational force:
• proportional to both masses.
• decreases as the inverse of the square of the
distance between the masses.
Weightlessness
Objects in orbit are in free fall. In free fall, you
experience weightlessness:
• you do have a gravitational force acting on you.
• there is no normal force. This is what leads to
the feeling of weightlessness.
Circular Motion
Instantaneous velocity is always tangent to
circle.
Circular Motion
Centripetal acceleration, points towards the
center of the circle.
Circular Motion
There is no centrifugal force pointing outward;
what happens is that the natural tendency of the
object to move in a straight line must be
overcome.
If the centripetal force vanishes, the object flies
off tangent to the circle.
tangent
Kepler’s Laws
Kepler’s laws describe planetary motion.
1. The orbit of each planet is an ellipse, with
the Sun at one focus.
Kepler’s Laws and Newton's Synthesis
2. An imaginary line drawn from each planet to
the Sun sweeps out equal areas in equal times.
Four Fundamental Forces
1. Gravity
2. Electromagnetism
3. Weak nuclear force
4. Strong nuclear force
Problem Solving – A General Approach
1. Read the problem carefully; then read it again.
2. Draw a sketch
3. List the known and unknown quantities
4. If the problem requires algebra, do the algebra first.
Once you are satisfied, put the numbers in.
5. Keep track of dimensions.
6. Make sure your answer is reasonable.