1. Topic
Submarine
Aim
To 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 pebbles
Pre-requisite knowledge:
Concept of buoyancy and Archimedes principle.
The working of a winding propeller
Newton’s third law of motion
Theory
The submarine works on the principle of buoyancy. When the side
tanks of the submarine are filled with water it sinks cos the weight of
the submarine equals the weight of the water displaced. And when it
comes to float it the water in the side tanks are displaced by air by
blowing air inside them. Air is less dense and weighs less than water. If a
submarine, even a huge one weighing sever tons, is in deep enough water, the air filled
submarine 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 propellers
functioning unit, rubber band, it gains elastic potential energy. As soon as it is released it
experiences a clockwise motion which creates two forces:

2. • 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.
Procedure
1
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.

3. 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.