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Circular Motion
When an object rotates or revolves around an axis.
Axis
Straight line through the center of motion about which the object moves.
Rotational Speed
Rate at which an object rotates or revolves.
Uniform Circular Motion
Constant rotational speed.
v=rw
linear speed = radius of revolution x rotational speed
Tangential Speed
“Tangent line“ will touch a curve at ONLY 1 point ex. giraffe in example
centripetal force
“center-seeking“ force that causes rotational movement.
centrifugal force
“center-fleeing“ force that “pushes“ rotating objects outwards.
rotational inertia
an object’s tendency to resist changes in rotational motion
rotational inertia depends on …
mass
size
shape
how the object rotates
torque
rotational analogue to force. “lever. “Torque seeks to change rotational motion. It occurs when a force pushes some object at some distance away from its axis of rotation
F (perpendicular) r, theta 90 → sin(90) → 1
torque = max when F (perpendicular) r
F (parallel) r, theta 0 → sin(0) → 0
torque = 0 when F (parallel) r
toque increases as …
theta approaches 90
torque is a vector which has …
direction
torque that seeks to cause counter-clockwise rotation is …
positive
torque that seeks to cause=clockwise rotation is …
negative
equilibrium
Fnet=0
balance
torque net=o
center of mass
average location of all mass in an object. For symmetrical objects, that is the objects center.
center of gravity
average point of an object’s weight
for the vast majority of cases CG=CM, but they’re technically different
.
CG WILL DETERMINE ______ FOR AN OBJECT
STABILITY
If ____ of an object os within the vertical of its base/supports, the object is said to be in stable equilibrium and will not fall over
CG
angular momentum
rotational analogue to linear momentum
ANGULAR MOMENTUM IS …
CONSERVED
if one quantity changes, the other must …
change the opposite way
ang mom. forms.
L=I x W, L=r x p
field force
does not exert force via physical contact. Instead, some quantity influences space around an object , creating a field. (for gravity this quantity is mass)
ex. sitting on a trampoline
you sit on a trampoline + deform its surface → field;
objects roll down into your dip → your field influencing them
gravity is…
purely attraction
Law Of Universal Gravitation
All objects with mass are gravitationally attracted to all other objects with mass, given by… Fg=G (m1xm2/d^2)
G = …?
6.67x10^11 N m^2/kg ^2
proportional to both masses
inversely proportional to separation squared
further apart → weaker
closer together → stronger
weight
Fg when rear planet’s surface
what we interpret as weight is actually normal force of ground supporting us
we can change how we feel we wight by changing N
ex: bathroom scale in elevator
when accelerating upwards, the scale will read greater than your weight
when accelerating downwards, the scale will read less than your weight
during free-fall, objects experience
Note
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