Newtons 2nd Law
if a net force DOES act on an object, it will change its motion (it will change its velocity or accelerate). The acceleration of an object is directly proportional to the net force action on the object and inversely proportional to the object's mass
Newtons 3rd Law
whenever one object exerts a force on another object, the second object exerts an equal and opposite force on the first object
equilibrium
when all forces are balanced, the net force is zero, either at rest or moving with constant velocity
normal force
the force exerted by one object on another
friction
a force that opposes motion by materials rubbing against each other
coefficient of friction
greek letter mu depends on the materials that are sliding against each other, the lower the coefficient, the lower the friction, has no units, just a value, will always be positive and less than 1
work
force times distance, not done on an object unless the object is moved due to a force, done when components of force are parallel to displacement, not done if the force is perpendicular to displacement
net force
the sum of all forces on an object
kinetic energy
energy of motion, depends on mass and speed
potential energy
stored energy
elastic potential energy
energy stored in any compressed or stretched object
gravitational potential energy
energy of an object due to its position relative to the gravitational source
mechanical energy
sum of kinetic energy and potential energy
power
the rate at which work is done
conservation of energy
in the absence of friction, the total amount of mechanical energy remais the same
momentum
a vector defined as the product of mass and velocity
impulse
the product of a constant force and the time over which it acts, this only applies when the force is CONSTANT
conservation of momentum
in all interactions between isolated objects, momentum is conserved. The TOTAL momentum remains constant for a system of objects that interact with each other
elastic collision
the two objects collide and then return to their original shapes with NO CHANGE in kinetic energy
inelastic collision
if objects collide and sound is produced, and they do not stick
perfectly inelastic collision
two objects hit each other and stick together with a common velocity after the collision
Newton's Law of Universal Gravitation
every two objects have a gravitation force between them
centripetal force
the force that maintains circular motion, never found alone, always equal to another force
centripetal acceleration
acceleration directed toward the center of a circular path
inertia
property of matter that resists changing motion
kepler's laws
1st law: planets move in elliptical orbits, 2nd law: planets sweep out equal areas in equal times, 3rd law: K has the same value for all planets
critical speed
the speed of an object must be moving in order to stay in a vertical circle
torque
a quantity that measures the ability of a force to rotate an object around some axis
lever arm
distance from turning axis to point of contact, perpendicular distance from axis of rotation to a line drawn along the direction of force
moment arm
same thing as lever arm
moment of inertia
resistance of an object to change its rotational motion
rotational equilibrium
when net TORQUE = 0
mechanical waves
waves that cannot exist without a medium
pulse wave
consists of one traveling pulse
periodic wave
wave whose source is some form of periodic motion
crest
highest point above equilibrium
trough
lowest point below equilibrium
hooke's law
f=kx
wave speed
distance through which each wave moves per second
wavelength
distance waves travel in one cycle (distance from crest to crest)
frequency
the number of cycles in a unit of time
amplitude
maximum displacement from equilibirum
transverse
when individual particles of a medium vibrate perpendicular to the direction in which the wave travels
longitudinal
when individual particles of a medium vibrate parallel to the direction of wave motion
constructive
when 2 waves of the same wavelength come together and crest meets crest and trough meets trough. The composite wave will have a greater amplitude than either wave
destructive
crest meets trough. composite wave is smaller than either of the original wave
hertz
unit for frequency
period
time it takes for one wave cycle
restoring force
the force acting in the opposite direction
simple harmonic motion
occurs whenever a force proportional to the displacement acts on a body in the opposite direction to its displacement from its normal position
pendulum
consists of a mass called a 'bob' on a fixed string of negligible mass
standing waves
occur when 2 waves of the same frequency, wavelength and amplitude travel in opposite directions and interfere with each other
resonance
when frequency of a force applied to a system matches the natural frequency of vibration of a system
pitch
frequency determines how high or low we perceive a sound to be
compression
part of a longitudinal wave where density and pressure are high
rearefaction
part of a longitudinal wave where density and pressure are low
ultrasonic
greater than 20,000 hertz
infrasonic
less than 20 hertz
intensity
rate at which energy flows through a unit area perpendicular to wave motion
doppler effect
althgouh the frequency of a siren remains the same at the source, the pitch is perceived to change because of relative motion between the observer and the wave source