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spontaneous bursting glass

Can you explain this?
We had a phenomenon happen recently(Tuesday the March 15th) about 8:30 PM that is inexplicable to us, but there must be some explanation. My wife & I were in separate rooms when we both heard an extremely loud noise from the living room! The noise sounded like a large glass that just hit a hard tile floor, but loudness was magnified.As it turned out we came into the living room to find a glass platter that we had sitting on the coffee table for about a year just shattered. –It broke completely by itself as there was no one in the room.
Do you know how this may have shattered/blew apart all by itself?We used the platter to put 3 little oil lamps on.
Inside our house the next morning at 6 AM we heard thunder outside so thought it might have had something to do with the barometric pressure.Very low barometric pressure & the type of glass it was made up combined just right to explode it like that? The temperature was a constant 68 degrees as it was for the months that was on the table.
If you have any idea about this, we would appreciate it.Thank you,
*I took some photos of the shattered platter. –will send them if you wish.


David H

Resistance and Resistivity

Simran Asked

“Two wires A and B of equal lengths,different cross-sectional areas and made of same metal a)name the property which is same for both the wires. b)name the property which is different for both the wires”


Since both the wires are of same metal, the resistivity will be same for both whereas since the dimensions (Area of cross section here) are different, the resistance will be different

Physics in Irrigation

Somnath asked:

“water in a canal 6m wide n1.5m deep is flowing with a speed of 10km/hr.How much area will it irrigate in 30min if 8cm of standing water is need”


Answer (to be posted soon)


The pressure exerted by a given force can be decreased by increasing the area of contact.


The equation shows that pressure is inversely proportional to area.


The foundation off building is made more broader than the rest of the building so that the pressure exerted by the weight on earth can be decreased.



The shoulder straps of school bags are made wider and soft so that the pressure exerted by the heavy bags on shoulders can be reduced. You can feel the paining pressure if you try to replace the broad strap with a narrow one.




The Military tanks have a broad chain so that the pressure exerted by the heavy vehicle on ground is a minimum and it can travel even through marshy places

  • Heavy Vehicles have more tyres
  • When vehicles get struck in marshy places, wooden planks are used for the vehicle to come up.
Try to add more via comments

Thrust and Pressure: Increasing pressure by decreasing Area

Thrust is defined as the force acting normal to a surface. Pressure is the thrust acting per unit area.


The equation suggests that the pressure is inversely proportional to area. We can increase the pressure for a given force by decreasing the area. Here are some examples.

Cutting Tools

Cutting tools have sharp edges with very low area so that high pressure

can be applied by a small force. You can realise this if you try to cut a tomato with a blunt knife and try again after sharpening it.

Nails and Drawing Pins

Nails and pins have sharp ends so that it can pierce into wooden boards and walls easily by applying a small force.

In a Karate Punch


In martial arts, the normal punch is executed in such a way that only two knuckles are hitting the target so that maximum pressure can be imparted.

If the entire flat portion of the fist is used, the pressure will be very much less and the opponent will not be hurt much. Punch is only just one of the many attacks in Karate. You can analyse the various attacks and blocks with a view to find the application of pressure in it.

TRY to find out more examples where we decrease area to increase pressure.

Pressure, area and railway tracks

Why the railway track are laid on large sized wooden or iron sleepers?

(SHARANYA  posted this question)


Trains have huge masses and rails are narrow. Therefore if they are directly put on earth, they will sink down due to the extreme pressure it would exert on earth when run over by the train. So they are laid on wooden or iron sleepers of large area so that pressure on earth is reduced.
Pressure = Force /Area.

As area increases pressure decreases.

What happens when we suck in water from a drinking straw that has a hole in it?And why?

Let’s first see what happens when we “suck” in water using a straw. We are actually reducing the pressure inside the  mouth. When we do not suck, the pressure on the surface of water and inside our mouth will be the same.

The Physics of Drinking with strawBut when we start to suck, the pressure inside the mouth is reduced and water is pushed into our mouth due to the greater pressure on the surface of water caused by the atmosphere.

If there is a hole, we are not able to produce a low pressure area inside our mouth by sucking in.

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