Further Mechanics Flashcards
(25 cards)
what is angular speed
the angle turned through per second (radians)
what is centripetal acceleration
as an object is moving in a circular path, its direction and therefore velocity is constantly changing. this is directed towards the centre and perpendicular to velocity.
what is centripetal force
for an object to follow a circular path a force must act on it. its also directed towards the centre and perpendicular to velocity
what can a centripetal force be
centripetal force is just a name for the inwards acting force when moving in a circular path. it could be friction, gravity or tension or all.
what is the centrifugal force
a fictitious force that opposes the centripetal force (outward force). in reality this is just inertia wanting to continue in a straight path.
what happens to an object moving in a circular path but the centripetal force gets removed
it will fly off in a straight line obeying newtons 1st law
what happens when a ball on a string is moving in a circular motion
at the top- CF= weight + tension
at the bottom T= CF + weight
what happens to forces on a car when at the top of the hill
centripetal acts downwards, weight acts downwards, reaction acts up. weight is larger than reaction
CF= weight - reaction
what happens to a car on top of a hill that “catches air”/ loses contact
the reaction force will be 0, so at that moment,
CF= weight
what are examples of simple harmonic motion
mass on a spring, simple pendulum
why do objects in SHM try to return to its equilibrium
a restoring force like tension or gravity will or friction
whats the definition of simple harmonic motion
An oscillation in which the acceleration of an
object is directly proportional to its displacement from its equilibrium position, and is directed towards the
equilibrium
what are the 3 key locations of SHM
equilibrium
max positive point
max negative point
what are the 6 key variables at each location during SHM
velocity
acceleration
kinetic energy
potential energy
force
displacement
what are the 3 important graphs of the motion of SHM do you need to know
displacement/time
velocity/time
acceleration time
when does time period for a pendulum not work
for angles greater than 10 degrees
what is a free vibration
objects oscillate at their natural resonant frequency. involves no transfer of energy to the surroundings
what is a forced vibration
where their is a periodic driving force which is applied at the driving frequency
what is resonance
when the driving frequency equals the natural frequency causing maximum energy transfer. very dangerous high amplitudes
what are the different amplitudes and phase differences for key driving forces
less than natural freq- small A (same a driver), 0 (in phase)
same as natural freq- huge A, pi/2
greater than natural freq, small A, pi (anti-phase)
how a guitars a good example or resonances being used with stationary waves
stationary waves are formed on the guitar, vibrations move little air so the sound is quiet. however the body of the guitar is designed to have natural frequency similar to the stationary waves, causing the large body to resonated moving a lot of air.
what is damping
in the real world oscillators experience a resistive force that removes energy from it. eg air resistance. they always act in the opposite direction of motion.
what are the 4 types of damping and what do they do
light damping- in air
heavy damping- in a liquid
critical damping- oscillations return to equilibrium as soon as possible
over damping- effectively heavy critical dmaping
how does damping work with resonance
in resonance- driving force=natural frequency.
damping can only reduce the size of the amplitude
