10A.4 Flashcards
what is free oscillation
the oscillation of a system, free from the influence of any forces from outside the system
what is natural frequency
the frequency of oscillation a system will take if it undergoes free oscillation
a free oscillation system
allows for a constant exchange of potential and kinetic energy
the exchange of energy in oscillation is caused by
a restoring force which is proportional to the displacement
what is forced oscillation
the oscillation of a system under the influence of an external (usually repeatedly applied) force
what is driving frequency
the frequency of an external force applied to the system undergoing forced oscillations
if you are forcing oscillations you are
adding energy to the system
when you add energy to the system in forced oscillations and that’s not done at the natural frequency it wont undergo
SHM and will dissipate energy quite quickly
what is resonance
very large amplitude oscillation that occurs once the driving frequency matched the natural frequency
when a system is forced to oscillate at its natural frequency it will
absorb more and more enegry
how can we investigate the resonant frequency
get a spring attach a hanging mass onto it, then attach a vibrations generator with a signal generator to the spring making the spring vibrate to different frequencies with all of the set up being held by a clamp and stand, then with the use of a motion sensor and a computer datalog find the different heights of mass at different frequencies(i.e monitor the amp of vibrations) until you find the max amplitude, the f at that amplitude will be the resonant frequency
after finding out the resonant frequency how may we find the mass of the hanging object, or the (springs) constant
by using the fact that t = 1/ f and with that f = 1/2pi√ k/m and rearrange to find m and k respectfully
what is a safety precaution we should take when investigating resonance
- use a stand clamped to the bench to hold the vibration generator
- use small mass and keep the vibrations small
what will happen to a pendulum amp if its left to swing
it will constantly decrease with each swing due to air resistance and the internal stresses within the flexing material of the string
what are damped oscillations
it is when work is on the damping system, and energy is dissipated in the damping system with each oscillation, so the amplitude of oscillation decreases
what is damping
a material, or system, causing energy loss during each damped collision for example attaching a small sail onto a pendulum so the air résistance can have a greater affect
what is underdamping
when the amplitude decreases exponentially and the oscillator completes several oscillations before stopping
what is overdamping
when the amplitude of oscillation drops very rapidly where it might not even complete one cycle (example: having the pendulum swing through a bowl of water)
what is critical damping
when damping is such that the oscillator would return to its eq position in the quickest possible time, without going past that position
what does a displacement against time graph look like for all types of damping (critical damping, underdamping, over damping, undamped)
page 161
how can we investigate damping
setting up a spring with hanging masses system held by stamp and clamed to the table, and with a motion senor with a computer datalog to measure the amp of vibrations, so after setting that up get a card sail that will act as an air resistance (it increases it). altering the size of the card would change the damping effect making the amp change and decrease more
what is a safety precaution when investigating damping
- make sure the spring is held securely in the clamp
2, only hang small mases
What can over damping be used in
car suspension systems, but too much overdamping could cause the oscillator to take a very long time to return to its original eq position
what is the solution for noise or problems that can be caused from a oscillator at its natural frequency
the solution is using a damping system whish differs from oscillator to oscillator
what is the best damping system called and its description and examples of it
the critical damping system (so that the system returns to its original eq position) which is specific for each use for example a clock needs to have a longer critical damping, while the bike needs to have a short one (i think so check with the sir)
how can we investigate damping solutions to design problems
by setting up a signal generator connected to a vibration generator to produce DRIVING FORCES (imp key word) with changeable frequency, and then using this to set up a model of an earthquake shaking a building and seeing how dampers could be attached to the model, internally or externally to reduce the damage caused by resonance
why should a climbing rope be both stretchy and stiff
it needs to be stretchy so that to avoid sudden painful stop, but stiff to bring the climber to a safe halt without hitting the ground
why does a climbing rope after the fall need to be plastically deformed
since the material is ductile the plastic deformation would reduce the amp of oscillation and it will provide critical damping, any less stiff material wont have enoughdamping to reduce the oscillations safely
during earthquakes steel framed building can
absorb the vibration energy since steal is ductile so its plastic deformation damps the oscillations
