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”
Answer:
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
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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)
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DECREASING PRESSURE BY INCREASING AREA
The pressure exerted by a given force can be decreased by increasing the area of contact.
P=F/A
The equation shows that pressure is inversely proportional to area.
FOUNDATION OF BUILDINGS
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.
SHOULDER STRAPS OF SCHOOL BAGS
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.
FEET OF ELEPHANT AND CAMEL
MILITARY TANK
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
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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.
P=F/A
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.
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