Transcript Newton`s Laws PPT

Newton’s laws
Ch. 12
Benchmark D: Explain the
movement of objects by applying
Newton’s three laws of motion.
 Grade
Nine
Forces and Motion
21. Demonstrate that motion is a
measurable quantity that depends on the
observer’s frame of reference and
describe the object’s motion in terms of
position, velocity, acceleration and time.
22. Demonstrate that any object does not
accelerate (remains at rest or maintains a
constant speed and direction of motion)
unless an unbalanced (net) force acts on
it.
MOTION & FORCES
A Force is a
PUSH or
PULL
“science never
‘sucks’!”
Balanced forces acting on a
body do not change the
direction of the object.
Inertia (1st law of motion)
…
is the resistance of an object to
a change in motion.
 Newton’s 1st law: an object in
motion will stay in motion or an
object at rest will stay at rest
UNLESS a force acts upon it!
23. Explain the change in motion
(acceleration) of an object.
 Demonstrate that the acceleration is
proportional to the net force acting on
the object and inversely proportional
to the mass of the object.
 (Fnet=ma. Note that weight is the
gravitational force on a mass.)

So, what does it all mean?
 Newton’s
second law states that the net
force causes an object to accelerate in the
direction of the net force,
 with an acceleration equal to the net force
divided by the mass.
 a = net Force/mass or F = ma
GRAVITY
 Gravity
is the force of attraction that exists
between 2 objects having mass.
The size of the
gravitational
force is
determined by
the mass of
the objects
AND their
distance apart.
Weight is…
 The
measure of the gravitational force
exerted on an object by Earth.
 Weight is expressed in “Newtons”
 W = m X 9.8 m/s2
 (where m is the mass of the object)
3rd Law of Motion Standard
 24.
Demonstrate that whenever one object
exerts a force on another, an equal
amount of force is exerted back on the first
object.
 (for
every action, there is an equal and
opposite reaction)
Third Law of motion…
 For
every action there is an equal and
opposite reaction.
 http://www.teachersdomain.org/asset/phy0
3_vid_asrnt/
 AKA...momentum!
Momentum
Calculate momentum…
p = mv
Where p is momentum, m
is mass and v is velocity
 When
2 objects collide, momentum can be
conserved.
 Some momentum from one object is
transferred to the other.