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Given below are certain situations in which variation in pressure is, brought about by increasing or decreasing the area of surface., Explain how these are useful., , * constructing a knife with a sharp edge., , A sharp knife cut objects better because due to its very, thin edge, the force of our hand falls over a very small area, of the object producing a large pressure and this large, pressure cuts the object easily., , * constructing buildings with wider basements., , The area in the basements is higher then the pressure, exerted by the buildings on the ground would automatically be, less., , * connecting the wheels of tanks and other such vehicles, using wide chains., , The weight of a tank is very high compared to a normal, vehicle. If wheels were,used the pressure/on the ground would, be so high that the wheels will go into the ground. So, to, decrease the pressure on the ground the wide chains are used, instead of wheels, , * making a sewing needle with a sharp tip., , The tip of the sewing needle is sharp so that due to its sharp, tip, the needle may put the force on a very small area of the, cloth, producing a large pressure sufficient to pierce the cloth, being stitched.