Longitudinal vibrations in solid metal rods

In summary: But with a hammer, you hold the tool at one end and hit the other end. You don't have a node in the middle!
  • #1
klng
22
0
Hi people,

I have a question which i hope you helpful guys/gals can help to shed light on.

We all know when we strike one end of a solid metal rod with a hammer sideways (i.e. from left to right), longitudinal vibrations will be set up across the length of the rod. Textbooks and websites always say that when we hold with our fingers in the centre of the rod, that location becomes a node.

My question is why does our fingers introduce a node? Are our fingers so strong that we can force every metal atom to remain still and not vibrate to and fro? Sounds a bit far stretched to me...

Thanks for the advice.
 
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  • #2
Hi, vibrations discontinue and becomes like a sine wave..so you there will be a node something..sometimes force on figures also matter..for e.g. in string musical instrument..
 
  • #3
Hi Rajini,

Thanks for the reply. But i guess it still doesn't address the question why the presence of the holding fingers force that location to become a node.

Any other responses from the experienced forummers please?

Thanks!
 
  • #4
Hi klng,
when you hold at a point..you will minimize the amplitude of the vibration at that point..
Node= zero amplitude and antinode=max. amplitude.
Is that okay..
 
  • #5
As you point out, striking a solid metal rod on the end with an axial hammer hit will induce a longitudinal compression wave in the rod that will reflect at the ends and reflect back and forth from end to end. Holding the rod in the center will damp all transverse resonant modes that do not have a node in the center. However, holding the rod in the center won't (I think) convert a longitudinal wave into a transverse wave. The lowest resonant transverse mode is a half-wave with maximum transverse motion at the ends, and with a node in the center. The next is a 3/2-wave mode.
Bob S
 
  • #6
Depends on the scenario. A long thin piece of metel - Yes - point of contact = node. But short strong piece of metel - No. Proof: hold a metel punch tool with your bare hands and hit it hard with a hammer! OUCH! It really hurts. The transverse forces go into your fingers.
 

What are longitudinal vibrations in solid metal rods?

Longitudinal vibrations in solid metal rods refer to the back-and-forth motion of particles in the metal rod along the direction of the wave propagation. These vibrations are caused by a disturbance or force applied to the rod, and travel through the material at a certain speed, known as the speed of sound.

What factors affect the speed of longitudinal vibrations in solid metal rods?

The speed of longitudinal vibrations in solid metal rods is affected by various factors, including the material properties of the metal (such as density and stiffness), the shape and size of the rod, and the temperature of the rod. These factors determine the speed at which the vibrations travel through the material.

How do longitudinal vibrations in solid metal rods differ from transverse vibrations?

Longitudinal vibrations involve particles moving back and forth along the direction of the wave propagation, while transverse vibrations involve particles moving perpendicular to the direction of the wave propagation. Additionally, longitudinal vibrations are typically faster than transverse vibrations, as the particles do not have to travel as far to complete one full cycle of vibration.

What are some practical applications of longitudinal vibrations in solid metal rods?

Longitudinal vibrations in solid metal rods have various practical applications, including in musical instruments (such as stringed instruments), earthquake detection and monitoring, and non-destructive testing in engineering and manufacturing industries.

How can longitudinal vibrations in solid metal rods be measured and analyzed?

There are various techniques for measuring and analyzing longitudinal vibrations in solid metal rods, including using accelerometers, laser or ultrasonic sensors, and strain gauges. These measurements can then be analyzed using signal processing techniques to determine the frequency, amplitude, and other characteristics of the vibrations.

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