Transcript Mechanical Equilibrium(star wars)

PHYSICS: Mechanical
Equilibrium
What usually comes to mind
then you hear the phrase:
“mechanical equilibrium”?
Imperial Walkers?
Mechanical, but
probably not…
PHYSICS: Mechanical
Equilibrium
What usually comes to mind
then you hear the phrase:
“mechanical equilibrium”?
Whiney Jedi?
Again, probably
not…
PHYSICS: Mechanical
Equilibrium
What usually comes to mind
then you hear the phrase:
“mechanical equilibrium”?
Asthmatic supervillains?
Awesome movie
effect, but no…
PHYSICS: Mechanical
Equilibrium
What usually comes to mind
then you hear the phrase:
“mechanical equilibrium”?
Duh, silly…
FORCE!
QUESTIONS AND ANSWERS
WITH EINSTEIN
Q: What is a force?
A: A force is any external push or
pull exerted on an object.
QUESTIONS AND ANSWERS
WITH EINSTEIN
Q: What forces are acting on
the book in the picture below?
normal force
weight
A: Weight and Normal
FORCES
FORCE – any external push or pull exerted on an
object
WEIGHT – the effect of gravity acting on the mass of
an object
• Weight could also be thought of as the force of gravity
NORMAL – the force of a surface pushing back on an
object
• A normal force is also known as a supportive force.
• A normal force is always PERPENDICULAR to the
surface.
FORCES
For some reason, I
always thought that
force was a power
that balanced out
good and evil in the
universe.
PHYSICS
According to GABE
What is a force?
FORCES
PHYSICS
Luke…use the force.
May the force be with
you…
I guess I gotta quit watching so
much T.V.
According to GABE
What is a force?
FORCES
NET FORCE – the combination of all forces acting
on an object
• Since force is a vector quantity, the direction of the forces
must be considered when figuring the net force.
EQUILIBRIUM – the fancy name for when the net
force equals zero
• Static Equilibrium occurs when an object is at rest.
• Dynamic Equilibrium occurs when an object is moving at
a constant velocity.
QUESTIONS AND ANSWERS
WITH EINSTEIN
Q: What type of motion is
occurring when the net force equals
zero?
A: Zero net force means that an
object is at rest. Thus, there is no
motion.
OR…
A: Zero net force could also mean
than an object is moving at a
constant speed.
FORCES
NET FORCE – the combination of all forces acting
on an object
• Since force is a vector quantity, the direction of the forces
must be considered when figuring the net force.
EQUILIBRIUM – the fancy name for when the net
force equals zero
FREE-BODY
DIAGRAM – a sketch used is to illustrate the forces
acting on an object
• Free-body diagrams use arrows to indicate the
magnitudes and directions of the forces.
QUESTIONS AND ANSWERS
WITH EINSTEIN
Q: What forces are acting on
the book in the picture below?
normal force
friction
weight
A: Weight, Normal, and Friction
QUESTIONS AND ANSWERS
WITH EINSTEIN
Q: Is there motion in this
situation? Is there a net force?
normal force
friction
weight
A: No motion implies that the net force equals zero.
FORMULAS FOR-m-U-las
Mathematical Version of Net Force
If an object is in a state of mechanical
equilibrium then the net force on the
object is zero:
F

0

NOTE: The “sigma” () notation means that you
need to “sum up” the forces.
FORCES
• Forces are vector quantities. This means that:
1) The direction is important (FBD helps here).
2) The magnitude may have components in two
dimensional situation (FBD helps here too).
3) Different forces acting on the same object can be
combined in differently to yield the net force.
EXAMPLE: Find the net force on the box. Assume it
stays on the ground.
20 N
10 N
30 N
FORCES
• Forces are vector quantities. This means that:
1) The direction is important (FBD helps here).
2) The magnitude may have components in two
dimensional situation (FBD helps here too).
3) Different forces acting on the same object can be
combined in differently to yield the net force.
EXAMPLE: Find the net force on the box. Assume it
stays on the ground.
20 N
10 N
10 N
FORCES
• Forces are vector quantities. This means that:
1) The direction is important (FBD helps here).
2) The magnitude may have components in two
dimensional situation (FDB helps here too).
3) Different forces acting on the same object can be
combined in differently to yield the net force.
EXAMPLE: Find the net force on the box. Assume it
stays on the ground.
10 N
10 N
0N
FORCES
• Forces are vector quantities. This means that:
1) The direction is important (FBD helps here).
2) The magnitude may have components in two
dimensional situation (FDB helps here too).
3) Different forces acting on the same object can be
combined in differently to yield the net force.
EXAMPLE: Find the net force on the box. Assume it
stays on the ground.
20 N
30°
17.3 N
FORCES
• Forces are vector quantities. This means that:
1) The direction is important (FBD helps here).
2) The magnitude may have components in two
dimensional situation (FDB helps here too).
3) Different forces acting on the same object can be
combined in differently to yield the net force.
EXAMPLE: Find the net force on the box. Assume it
stays on the ground.
20 N
30°
10 N
27.3 N
PHYSICS
IS
PHUN!