13. Oscillations Flashcards
What happens it an object is experiencing simple harmonic motion?
- It experiences a restoring force which acts towards the centre of equilibrium.
- Its force is directly proportional to the object’s distance from equilibrium.
What is amplitude?
The maximum displacement of an oscillating system
What is time period?
Time take for one full cycle of an oscillating system.
e.g.
Equilibrium to amplitude.
Then amplitude to equilibrium.
What is the restoring force?
A force that acts towards the equilibrium.
What is true about the acceleration of an object experiencing SHM?
It’s acceleration is directly proportional to is displacement and is in the opposite direction.
a = -ω²x
What is angular velocity?
The angle an objects moves through per unit time.
ω = 2πf
What effect the time period of these simple harmonic systems?
- Simple pendulum
- Mass-spring system
Simple pendulum: mass and length of spring.
- Mass-spring system:
mass and spring constant.
Describe the graph of displacement against time of a SHsystem.
Sinusoidal
- starting at (+)amplitude.
Describe the graph of velocity against time of a SHsystem.
Sinusoidal
- starting at 0
(its the gradient function of dis-time)
Describe the graph of acceleration against time of a SHsystem.
Sinusoidal
- starting at (-)amplitude.
(its the gradient function of velo-time)
What is resonence?
Where the amplitude of an oscillating system increases due to gaining an increased amount of energy from the driving force.
When does resonance occur?
When the driving force is equal to the natural frequency of the system.
How do you decrease the effects of resonance?
Dampening.
What is dampening?
- Where a force acts on an oscillating system and energy is lost from the system to its environment.
- Leading to a reduced amplitude.
When can oscillating systems lose/gain energy?
When an external force acts on it.
What is true of an undamped system?
- There are no external forces acting.
- No energy is lost to the environment.
- Total energy of the system remains constant.
Describe the change in energy of a SHsystem.
- At amplitude the system has maximum potential energy.
- As moves to equilibrium, PE is converted to kinetic energy.
- At centre of oscillation KS is at a maximum.
What are free vibrations?
- When there is no external force that is continuously acting on a system.
- Thus the system oscillates at its natural frequency.
What are force vibrations?
- When a system experiences an external driving force which causes it to oscillate.
- Its frequency is known as the driving frequency.
What are the three types of damping?
- Over.
- Critical.
- Under.
What is under damping?
- Where the amplitude gradually decreases by small amounts each oscillation.
- Graph of diminishing sinusoidal wave.
What is critical damping?
- Where the amplitude reduces to zero in the shortest possible time without oscillating.
- Starts at maximum and curves to zero rapidly.
What is over-damping?
- Where the amplitude reduces slower than critical damping but without any additional oscillations.
- Starts at zero and curves to zero over time.
What happens to the amplitude once the degree of dampening increases?
It decreases.
What is a ductile material?
One that can undergo a large amount of plastic deformation before fracturing.
Why can a ductile material be used in dampening?
- it can reduce the amplitude of oscillation
- because energy is used to defor the material.
- decreasing the KE of the system.
- so decreasing the amplitude of oscilation.
