Build a Boat
Problem statement: Build a boat that can carry 50gms weight across 2ft. There is no restriction on the length, width or height of the boat.
Introduction :
Buoyancy is the property of an object to float in a liquid or gas ex: water or air. When any object is placed in water, the water pushes back on it. This upward force from water is called the buoyant force. On the other hand, gravity pulls the object down, making it heavy.
If the upward push from water ie: the buoyant force is stronger than the downward pull of gravity, the object floats. If the downward pull of gravity is stronger than the buoyant force, the upward push from the water, the object sinks.
Different factors affect the buoyancy of objects.
Density: The quantity of “stuff” packed into the volume of an object (its density) affects buoyancy of the object. Less dense objects are more likely to float, while more dense objects are likely to sink fast. Ex: Between Styrofoam and stone of same size, styrofoam floats while stone sinks.
Displaced Fluid: When you put an object in water, it pushes some water out of the way (it “displaces” it). The more water an object pushes away, the stronger the upward push it gets, and the more likely it is to float. Ex: The shape of a boat is designed to have high empty volume to displace more water and have better buoyancy.
Materials Provided:
- The material that will be provided is
- Straws – 30
- Popsicle / Icecream Sticks, 11cms – 30
- Skewer sticks – 10
- Fevicol Squeeze bottle 45gms – 1
- Thread – 4 mtrs
- Millipore tape small – 1 per team
- Cellotape – On request
- Rubber bands small – 10
- Rubber bands medium – 10
- Cardboard – 1
- Icecream Spoon – 2
Materials students are permitted to bring along:
- Printout / hand drawn diagram of the model they plan to build, as a sheet or notebook.
- Stationary like Scale, Scissor etc. to help with their build(This material cannot be part of the built boat model).
- Colouring / decoration material.(This material cannot impact the functioning of the boat)
Activity Description:
Build a boat that can carry 50 gms weight across 2ft. There is no restriction on the length, width or height of the boat.
What aspects to consider while defining the shape of the boat?
Increase Surface Area: A larger, wider boat can float with more weight because it pushes up more water, creating a stronger buoyant force.
Add Depth: Making the boat walls taller and deeper helps to keep the water out and increases the volume of air inside, making the boat more stable. Like the multilayer boat in this video. The upper straws can also be secured with millipore tape to prevent water from entering them. But because of its bulky nature, this boat model will be slow.
Consider Shape: Experiment with different shapes, like a narrow, fast catamaran versus a wide, deep traditional hull, to see how shape affects speed and carrying capacity.
Stability: A boat needs to be stable to hold weight. Distribute weight evenly across the boat to prevent it from tipping.
Words of Caution : 1. Materials that soak in water should be as far away from water as possible. Ex: Cardboard. 2. While using straws in building the boat model, as long as water does not enter into the straws , the air cavity in the straws helps the boat stay afloat even when weights are loaded. 3. The way Cellotape and Millipore tape work is different in water.
Testing strategy:
Testing will be done in 2 stages.
Stage 1 testing : All the boat models that can hold 50gms weight will be tested for.
Stage 2 testing : The models that are able to hold atleast 50gms will be tested for the time it takes to move 2 ft with a load of 50gms. Kids will use Icecream spoons as paddles to manually move the boat.
Stage 1 and Stage 2 will be repeated by increasing the weights by 10+ gms.
| Coin Denomination | Weight in gms |
| New Rs. 1 | 3.09 |
| New Rs. 2 | 4.07 |
| New Rs. 5 | 6.74 |
| New Rs. 10 | 7.74 |
50 gms ~ 5*New Rs. 1 + 5*New Rs. 5 coins
Every 10+ gms ~ New Rs. 2 + New Rs. 5 coins