Download Motion and Forces

Wednesday November 4, 2015
Unit Question What role do forces play in the world
around us?
Guiding
How do Newton’s Laws affect
Question /
everyday objects?
Learning Target
Warm-up
Which of Newton’s Laws
is responsible for this
situation?
1st Law: An object in
motion stays in motion
Agenda
Homework
1. Forces Notes and Diagrams
2. Ramp Demonstration
1. Quiz Friday
What is a Force?
• Force – push or pull one body
exerts on another
What is a Force?
• Force is measured using the standard
metric unit known as the Newton (N).
• One Newton is the amount of force
required to give a 1-kg mass an
acceleration of 1 m/s/s. Thus, the
following unit equivalency can be
stated:
– 1 Newton = 1 kg • m/s2
• A force is a vector quantity.
• A vector quantity is a quantity that
has both magnitude (size) and
direction.
• Net force – the combining of
forces when two or more forces
act on an object
• Balanced forces – forces that are
equal in size and opposite in
direction
– Forces are acting on the same
object
– Do not cause the motion of the
object to change
• Unbalanced forces – forces that
are not equal and/ or opposite in
direction
– Net force causes object to move in
direction of force
Unbalanced
Balanced
How does the rocket fly?
• Unbalanced
Forces!
How are these not balanced forces?
• Because
the object
is
moving!
Common Forces
• Gravity – the attraction two objects
have for one another
• Air resistance – opposing force an
object feels when traveling
through air
• Friction – resistance to motion
caused by two objects in contact
with one another.
Exit Question
• Which way will this block move?
Newton’s Labs
• Go to your assigned station.
• Do not move until instructed to do
so.
Inertia and Mass
• Inertia – the tendency of an object
to resist changes in its motion
– The greater the mass of an object
the greater its inertia
• Newton’s First Law of Motion –
‘Stuff keeps doin’ what its doin’
until somethin’ else messes with
it…’
Check it out…
http://www.batesville.k12.in.us/physics/PhyNet/M
echanics/Newton1/The_Net_Force.html#NetF
orceQuiz
F=mxa
• Force, mass,
and acceleration
are all
connected.
– For any object,
the greater the
force applied to
it, the greater its
acceleration will
be.
Learning Checkpoint
• If two equal forces act on an
object in opposite directions,
what is the acceleration?
• According to balanced forces,
the acceleration of the object
would be zero.
Learning Checkpoint
• Calculate the force on an
object that has a mass of
12 kg and an acceleration
of 4 m/s/s.
• F = mx a
• F = 12 kg x 4 m/s/s
• F = 48 kg x m/s/s = 48 N
Learning Checkpoint
What is the acceleration of a
200 kg object with 3,000 N of net
force acting on it?
a=F/m
a = 3,000 kg x m/s/s / 200 kg
a = 15 m/s/s
Newton’s Third Law
• When one object exerts a force
on a second object, the second
one exerts a force on the first
that is equal in size and
opposite in direction.
– “To every action, there is an equal
and opposite reaction.”
– Example – when you jump on a
trampoline the trampoline exerts the
same force on you in the opposite
direction.
Learning Checkpoint
• When a force is exerted on
a box, an equal and
opposite force is exerted by
the box. These forces are
known as _____ forces.
• These forces are actionreaction forces.
Learning Checkpoint
• What is the difference
between weight and mass?
• Mass is a measure of the
amount of matter in an object,
while weight is a measure of
the force of gravity on the
object’s matter.