Damping & Plastic Deformation (Edexcel International A Level Physics)

Damping & Plastic Deformation

• Damping an oscillator affects its amplitude of oscillation: 

  • When damping is increased the amplitude decreased

  • damping and amplitude are inversely proportional to each other

As damping is increased, resonance peak lowers, the curve broadens and moves slightly to the left

• A Ductile material can be stretched for a long time before it snaps

  • We can say it undergoes a large amount of plastic deformation before it is permanently deformed

• Examples of ductile materials include:

  • Most metals (particularly copper, gold and silver)

  • Non-metals are generally not ductile

Brittle and ductile materials on a stress-strain graph. These are the same on a force-extension graph too

• The amplitude of oscillations can be reduced due to the plastic deformation of a ductile material

• This happens because energy from the oscillations is used to deform the material

  • The kinetic energy of the oscillator is reduced and transferred into the deformation of the material

• A climbing rope is different from a rescue rope or a bungee cord:

  • A climbing rope is designed to extend when loaded suddenly

  • The rope stretches to reduce the amplitude of the oscillation when a climber falls onto it 

  • It provides critical damping by immediately stopping the climber from bouncing

A climber uses a dynamic rope that stretches when she falls onto it. This reduces the amplitude of her oscillation and the force she experiences reducing injury.