TopicSubmarineAimTo prepare a simple model of a submarine.Materials required 1. Large plastic bottle, 2. two small plastic bottles, 3. scissors , 4. 2 plastic straws , 5. rubber band , 6. m-seal , a bulldog clip 7. tissue papers , 8. paint colors , 9. paper cutter, 10.Araldite/any water proof glue 11.Plastic cardboard/steel wire 12.Sand and pebblesPre-requisite knowledge:Concept of buoyancy and Archimedes principle.The working of a winding propellerNewton’s third law of motionTheoryThe submarine works on the principle of buoyancy. When the sidetanks of the submarine are filled with water it sinks cos the weight ofthe submarine equals the weight of the water displaced. And when itcomes to float it the water in the side tanks are displaced by air byblowing air inside them. Air is less dense and weighs less than water. If asubmarine, even a huge one weighing sever tons, is in deep enough water, the air filledsubmarine will float since it weighs less than the water around it.The work of a propeller is to bring an object in motion. When we wind the propellersfunctioning unit, rubber band, it gains elastic potential energy. As soon as it is released itexperiences a clockwise motion which creates two forces:
• An upward force on water • And downward force on the submarine Fwater displaces water in, say, A direction then by the third law of motion the Fsubmarine works into her opposite direction B and hence submarine moves forward. Introduction Project description in this project you will study the forces that make a submarine go under water and come back up to the surface. Procedure1 Take the 2 small bottles and make an opening of about 1.5*1.5cm^2 area in each of them. This would be the entrance-exit for water. Pierce another hole directly above this opening and insert a straw into it, seal them using M-seal. And then tape these two straws together. This is from where we’ll blow air into the bottles. 2 Now take the big bottle. Cut two rectangles, from the cardboard, of about 2.5*4 cm^2 area and attach them at the base of bottle on left-right sides,( assuming bottle placed horizontally). 3 Now attach the other two bottles on either sides of the big bottle using araldite keeping the straws above and ‘opening’ below considering the setup placed flat on the surface. 4 Now wind the steel wires around the side cardboards and then draw it till the mouth of the small bottles and wind the other free end. This would keep the cardboards fix at considerable distances giving way for the propeller to move. 5 To make Propeller: • From the cardboard cut two rectangles of about 1inch in width and length such that it remains at rotatable distance from the left-right cardboards. • Now make a slit in each of them and fix into each other. • Then take a rubber band and fix it using araldite at two alternate parts of the propeller out of four leaving the ends from where you stretch rubber band opened. • The propeller’s ready! 6 Now attach the ends of the rubber band to the side cardboards making the propeller stretch.
7 Don’t forget to seal the mouths of the side bottles with their caps.8. Now fill sand and pebbles into the large bottle.9 Visit your imagination and paint it as you wish. Our submarine is ready! Working/Observations: • Before placing the submarine in water seal the straws’ mouth using the bulldog clip. This would prevent water from getting inside the bottles. And help the submarine to float. Reason: The water enters the bottles from the opening and pushes air out through the straws. However when we seal the mouth there is no space for air to leave and hence water cannot enter. • Place the submarine and then wind the propeller. When we’ll leave the propeller submarine will move forward. Reason: Stated in the theory. • To sink the submarine, remove the clip. Reason: This would provide exit for air and hence water would enter the bottles increasing weight and sinking the submarine. • To bring the submarine to a certain level, blow air into the straws and then seal it. Reason: The blown air pressure would expel water out and reduces the weight. Precautions: • Ensure the sand doesn’t accumulate at one side, this could make the bottle vertical. • Seal all the unnecessary openings properly. • Provide considerable distance for the propeller to rotate.