Dimensions must be the same on
both sides of the equals sign
Because of that we
know time does not =
speed x distance
mgh doesn't = 1/2mv^2
Vectors
Can either add, multiplied by
scalar, subtract, or resolved
into components
An arrow indicates the
magnitude of the vector
The direction of the arrow
indicates the direction of the vector
with respect to a given coordinate
system
Vector Components
Fx = Fcos(angle)
Fy = Fsin(angle)
Chapter 2
Aristotle's Mechanics
celestial vs. terrestrial motion
v=F/R (INCORRECT)
What is Motion?
Velocity and Speed
Velocity is a vector, with
speed being its magnitude
velocity=displacement/time
instantaneous: velocity at a single point
in time (slope of position vs. time graph)
Acceleration
change in velocity/change in time
Inertia
Galileo's experiment with an inclined
surface set the cornerstone for the
principle of intertia
Newton's Laws of Motion
LAW #1: If the total force acting on an object is
zero, the object will maintain its velocity forever
LAW #2: Total force acting on an object
is the sum of all of the forces acting on
that object
F=ma
1N=1kgm/s^2
LAW #3: When one object exerts a force on second object, the
second object exerts a force of the same magnitude and opposite
direction of the original force
An object's resistance to motion
Redefining Aristotles 'Laws'
Reworking Theories is vital
Motion with constant acceleration
v +Vi +at
Normal Forces and weight
Apparent weight
N = mg + ma
Mass
F gravity = -mg
Free Body Diagrams
recognize objects of interest
Sketch!
Identify Relationships
Solve!
Chapter 3
AIr Drag
Depend on Shape of Object
Larger for Objects Moving at high speeds
Bacterium
Drag force large compared to weight
Frictiojn
Kinetic Friction
Force against the force needed to continue moving an object on a surface
Static Friction
Force against the force needed to begin moving an object on a surface
F=uN
Free Fall
Initial velocity equals zero under standard conditions
a=gravity (9.8m/s^2)
g is positive or negative depending on the direction of the vertical motion
Tension
T=mg+ma
For a pulley system, Tension opposes mass and gravity
Chapter 4
Statics
Translation equilibirum
velocity and acceleration are both zero
Ex) tight rope walker, tensions are in equilibrium
Static Equilibrium and frictional Forces
Example: for a car on a hill not to move normal force, mg, and friction must add to zero
Projectile Motion
motion of arrow, ball or rock when it is thrown
Car rolling off a cliff. Car's velocity vector is always tangent to the tragectory
the time the car takes to reach the ground is independent of the motion along x