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• 1. WHY CAMEL CAN RUN IN A DESERTEASILY?WHY AN ARMY TANK WEIGHING MORETHAN A THOUSAND TONNE RESETSUPON A CONTINUOUS CHAIN?WHY CUTTING TOOLS HAVE SHARPEDGES?
• 2. THE NET FORCE IN APARTICULAR DIRECTIONIS KNOW AS THRUSTTHE FORCE PER UNITAREA IS KNOW AS PRESSURE
• 3. YOU WISH TO FIX A POSTER ON A BULLETIN BOARD.TODO THIS TASK YOU WILL HAVE TO PRESS DRAWING PINSWITH YOUR THUMB.YOU APPLY FORCE ON THE SURFACEOF THE HEAD OF THE PIN.THIS FORCE IS DIRECTEDPERPENDICULAR TO THE SURFACE AREA OF THEBOARD.THIS FORCE ACTS ON A SMALLER AREA AT THE TIPOF THE PINYOU STAND ON LOOSE SAND.YOUR FEETGO DEEP INTOTHE SAND.NOW,LIE DOWN ON THE SAND.YOU WILL FINDTHAT YOUR BODY WILL NOT GO THAT DEEP IN THESAND.IN THE BOTH CASE THE FORCE EXERTED ON THESAND IS THE WEIGHT OF YOUR BODY.
• 4. THE FORCE ACTING ON AN OBJECTPERPENDICULARLY IS CALLED THRUST.THE FORCE ACTING ON AN OBJECT PERUNIT AREA IS CALLED PRESSURE.PRESSURE IN A SMALL AREA IS MORE.PRESSURE IN A LARGER AREA IS LESS.
• 5. SUBSTITUTING THE SI UNIT OF THRUST AND AREA INEQ,WE GET THE SI UNIT OF PRESSURE AS
• 6. A BLOCK OF WOOD IS KEPT ON A TABLETOP.THE MASSOF WOODEN BLOCK IS 5kg AND ITS DIMENSIONS ARE40cm*20cm*10cm.FIND THE PRESSURE EXERTED BYTHE WOODEN BLOCK ON THE TABLE TOP IF IT ISMADE TO LIE ON THE TABLE TOP WITH ITS SIDES OFDIMENSIONS (A)20cm*10cm AND (B) 40cm*20cm.
• 7. A NAIL HAS A POINTED TIP.KNIVES HAS SHARP EDGE.BUILDING HAVE WIDEFOUNDATIONS.BUSES HAVE WIDE TYRES.CAMEL HAS FLAT LEG.HUMANS HAS FLAT PLAMS.
• 8. ALL LIQUIDS AND GASES ARE FLUIDS.A SOLIDSEXERTS PRESSURE ON A SURFACE DUE TO ITSWEIGHT.SIMILARLY,FLUIDS HAVE WEIGHTS,ANDTHEY ALSO EXERT PRESSURE ON THE BASE ANDWALLS OF THE CONTAINER IN WHICH THEY AREENCLOSED.PRESSURE EXERTED IN ANYCONFINED MASS OF FLUID IS TRANSMITTEDUNDIMINISHED IN ALL DIRECTIONS.
• 9. You ever drawn water from a well andfell that the bucket of water is heavierwhen it is out of the water?You ever wondered why a ship made ofiron and steel does not sink in seawater,but while the same amount ofiron and steel in the form of a sheetwould sink?You ever had a swim in a pool andfelt lighter?
• 10. TAKE AN EMPTY PLASTIC BOTTLE.CLOSE THE MOUTH OF THE BOTTLE WITH ANAIRTIGHT STOPPER.PUT IT IN A BUCKET FILLED WITH WATER.YOU SEE THAT BOTTLEFLOAT.PUSH THE BOTTLE INTO THE WATER.YET FEEL AN UPWARD PUSH.TRY TO PUSH ITFURTHER DOWN.YOU WILL FIND IT DIFFICULT TO PUSH DEEPER AND DEEPER.THISINDICATES THAT WATER EXERTS A FORCE ON THE BOTTLE IN THE UPWARDDIRECTION.THE UPWARD FORCE EXERTED BY THE WATER GOES INCREASING AS THEBOTTLE IS PUSHED DEEPER TILL IT IS COMPLETELY IMMERSED.NOW,RELEASE THE BOTTLE.IT BOUNCES BACK TO THE SURFACE.DOES THE FORCE DUE TO THE GRAVITTATIONAL ATTRACTION OF THE EARTH ACT ONTHIS BOTTLE?IF SO,WHY DOESN’T THE BOTTLE STAY IMMERSED IN WATER AFTER IT ISRELEASED?HOW CAN YOU IMMERSE THE BOTTLE IN WATER?
• 11. THE FORCE DUE TO THE GRAVITATIONAL ATTRACTION OF THE EARTHACTS ON THE BOTTLE IN THE DOWNWARD DIRECTION.SO THE BOTTLE ISPULLED DOWNWARD.BUT THE WATER EXERTS AN UPWARD FORCE ONTHE BOTTLE.THUS,THE BOTTLE PUSHED UPWARD.TO KEEP THE BOTTLE COMPLETELY IMMERSED,THE UPWARD FORCE ONTHE BOTTLE DUE TO THE WATER MUST BE BALANCED.THIS CAN BEACHIEVED BY AN EXTERNALLY APPLIED FORCE ACTING DOWNWARD.THSFORCE MUST AT LEAST BE EQUAL TO DIFFERENCE BETWEEN THEUPWARD FORCE AND THE WEIGHT OF THE BOTTLE.
• 12. WEIGHT OF AN OBJECT IS THE FORCE DUE TO GRAVITATIONALATTRACTION OF THE EARTH.WHEN THE BOTTLE IS IMMERSED,THE UPWARD FORCE EXERTEDBY THE WATER ON THE BOTTLE IS GREATER THAN ITS WEIGHT.THEREFORE IT RISES UP WHEN RELEASED.THE UPWARD FORCE EXERTED BY THE WATER ON THE BOTTLE ISKNOWN AS UPTHRUST OR BUOYANT FORCE.IN FACT,ALL OBJECTS EXPERIENCE A FORCE OF BUOYANCY WHENTHEY ARE IMMERSED IN A FLUID.THE MAGNITUDE OF THISBUOYANT FORCE DEPENDS ON THE DENSITY OF THE FLUID.
• 13. TAKE A BEAKER FILLED WITH WATER.TAKE AN IRON NAIL AND PLACE IT ON THE SURFACE OF THEWATER.OBSERVE WHAT HAPPENS.THE NAIL SINKS.THE FORCE DUE TO THE GRAVITATIONAL ATTRACTIONOF THE EARTH ON THE IRON NAIL PULLS IT DOWNWARDS.THERE ISAN UPTHRUST OF WATER ON THE NAIL,WHICH PUSHES ITUPWARDS.BUT THE DOWNWARD FORCE ACTING ON THE NAIL ISGREATER THAN THE UPTHRUST OF WATER ON THE NAIL.SO IT SINKS.
• 14. TAKE A BEAKER FILLED WITH WATER.TAKE A PIECE OF CORK AND AN IRON NAIL OF EQUAL MASS.PLACE THEM ON THE SURFACE OF THE WATER.OBSERVE WHAT HAPPENS.THE CORK FLOATS WHILE NAIL SINKS.THIS HAPPENS BECAUSE OF THEDIFFERENCE IN THEIR DENSITIES.THE DENSITY OF A SUBSTANCE ISDEFINED AS MASS PER UNIT VOLUME.THE DENSITY OF CORK IS LESSTHAN THE DENSITY OF WATER.THIS MEANS THAT THE UPTHRUST OFWATER ON CORK IS GREATHER THAN THE WEIGHT OF THE CORK.SO ITFLOATS.