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Q: I you put an alarm in a vacuum jar you can't hear it why?
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If an alarm clock is in a jar filled with air what happens if all the air sucked out of the jar?

The alarm would be much quieter, as sound can't travel through vacuum. But if it's a mechanical alarm clock then vibrations would be transferred from the clock to the jar and then to whatever the clock is standing on , and you'd probably be able to hear some of that.


Why cant you hear a bell inside of a vacuum jar?

Sound is mechanical energy, and the energy of the sound is transferred into the medium through which it is travelling. As the energy of sound is carried by the medium, the vacuum of space will not support a sound wave.


What are the jobs in the bell jar experiment for the foam block and vacuum pump?

The vacuum pump stops the sound waves from coming out. Because there are no particles to pass on the sound in a vacuum, we see the clock vibrating, but do not hear anything at all.


How can you show that sound is a form of mechanical energy?

Sound can only travel through a medium (matter). Different materials allow sound to travel faster or slower. However, as an experiment put an electron bell in a bell jar. You hear it ring. Evacuate the bell jar of as much gas a possible ( a true vacuum is almost impossible to achieve in a Bell Jar), allow the bell to ring again. It will be much quieter, although the bell hammer will be vibrating at the same speed. By extrapolation, when all the gas is evacuated(vacuum) there will be no sound. So sound needs a medium to travel through.


Experiment to demonstrate that sound need a material medium to propagate?

Take an electric bell and hang this bell inside an empty bell-jar fitted with a vacuum pump (as shown in the following figure). Initially, one can hear the sound of the ringing bell. Now, pump out some air from the bell-jar using the vacuum pump. It will be observed that the sound of the ringing bell decreases. If one keeps on pumping the air out of the bell-jar, then at one point, the glass-jar will be devoid of any air. At this moment, no sound can be heard from the ringing bell although one can see that the prong of the bell is still vibrating. When there is no air present inside, we can say that a vacuum is produced. Sound cannot travel through vacuum. This shows that sound needs a material medium for its propagation.

Related questions

If an alarm clock is in a jar filled with air what happens if all the air sucked out of the jar?

The alarm would be much quieter, as sound can't travel through vacuum. But if it's a mechanical alarm clock then vibrations would be transferred from the clock to the jar and then to whatever the clock is standing on , and you'd probably be able to hear some of that.


Will you hear anything when you set the alarm clock on the table and place it under a bell jar?

yes, because the bell jar will vibrate


Why cant you hear a bell inside of a vacuum jar?

Sound is mechanical energy, and the energy of the sound is transferred into the medium through which it is travelling. As the energy of sound is carried by the medium, the vacuum of space will not support a sound wave.


What are the jobs in the bell jar experiment for the foam block and vacuum pump?

The vacuum pump stops the sound waves from coming out. Because there are no particles to pass on the sound in a vacuum, we see the clock vibrating, but do not hear anything at all.


Why can a safety button on a jar not be clicked before it is opened?

The vacuum inside the jar keeps the button down. On opening the jar, the vacuum is broken and the button pops up (and the lid can be clicked). Therefore, if the safety button is up, the vacuum seal has been broken and the contents of the jar may have been contaminated, and the contents may have gone off!


5 On some food jar tops there is a message that the buttons will pop-up when the jar is open How does this work?

During packaging, a vacuum was created inside the jar, pulling the button in. When the jar is opened, the vacuum is released which allows to button to return to the "popped up" position.


If a bell is ringing in a bell jar you cant hear it when the air is pumped out but you see it what differences in properties of sound and light does this indicate?

That sound cannot move through a vaccum.


Why can't you hear whoosh sound when you open the jar of pickle or peanuts at the second time or can you hear the sound at the second time?

Jars of peanuts, pickles, spaghetti sauce and others, are vacuum sealed at the manufacturing plant. That means that all the air is sucked out of the jar at the moment that the lid is screwed on. This is done to prevent bacterial growth. the whoosh sound we hear is the outside air rushing back into the jar when we open it for the first time. When we close the jar, there is always some air that stays trapped in the empty space under the lid. Since air is already present in the jar when we open it again, no air needs to rush in and no whoosh sound is produced.


Cite an experiment to show that sound needs a material medium for its propagation?

Obtain a bell jar with a valve at the top, place the bell jar on a smooth flat surface. connect the valve to a vacuum pump through a rigid hose. Place a manual wind up spring alarm clock under the bell jar. Seal the bottom lip of the bell jar with petroleum jelly and ensure there are no gaps between the bell jar and the surface. Note the ticking of the clock. Start the vacuum pump and observe when the internal pressure begins to drop. Stop the vacuum pump and close the valve. Listen to the clocks ticking. Re start the vacuum pump and note the pressure drop, close the valve and listen to the ticking clock. As the pressure decreases the sounds of the clock will get fainter and fainter because there is less of the material medium (Air) to transfer the sound.


Why doesn't the seal on a mayonnaise jar hiss when you open it?

It's not under pressure (caused by gas) or in a vacuum. You should be concerned enough not to eat it if you hear a sound. The reason is that spoilage can give off gases.


What is the function of bell jar?

A bell jar is a glass dome that can house delicate objects or serve as a vacuum if the air is sucked out.


Describe the bell in a bell jar with vacuum experiment?

A bell jar is a piece of laboratory equipment used for creating vacuums.[1] It can be similar in shape to a bell, and can be manufactured out of a variety of materials (ranging from glass to different types of metals). A bell jar is placed on a base which is vented to a hose fitting, which can be connected via a hose to a vacuum pump. By pumping the air out of the bell jar, a vacuum is formed.