How Things Work

Given: We need to think about whether all objects can spin and list some that can.

Concept: Spinning means rotating around a central point or axis. Objects that are round, balanced, or have a pointed base tend to spin well.

Answer: No, not all objects can spin easily. Objects that are round, symmetrical, or have a smooth surface spin better.

Objects that can spin:
1. Top (spinning top / lattu)
2. Coin
3. Ball
4. Wheel
5. Bangle
6. CD or disc
7. Globe
8. Fan blades

Final Answer: Not all objects can spin. Rounded, symmetrical objects like coins, tops, bangles, and balls spin well.

Given: We spin different objects and record observations, questions, and thoughts.

Concept: When objects spin, they behave differently based on their shape, weight, and balance. Symmetrical and round objects spin longer and more smoothly.

Completed Table:

Coin:
- I observe: As it slows down, it begins to shake and wobble before falling flat.
- I wonder: Why does it start to shake as it slows down?
- I think: As it loses speed, it cannot balance itself upright anymore, so it wobbles and falls.

Bangle:
- I observe: As time passes, the sound becomes louder and faster just before it stops.
- I wonder: Why does the sound change as it slows down?
- I think: As the bangle tilts more and hits the surface more frequently, the sound increases before it stops.

Pencil:
- I observe: The pencil does not spin smoothly; it wobbles and falls quickly.
- I wonder: Why does the pencil not spin as long as a top?
- I think: Because the pencil is not perfectly round or balanced, it cannot spin steadily.

Piece of Stone:
- I observe: The stone barely spins; it just rolls or tips over immediately.
- I wonder: Why can't a stone spin like a top?
- I think: Because a stone has an irregular shape and is not balanced, it cannot spin properly.

Wooden Spinner (Top):
- I observe: The top spins smoothly for a long time and stays upright while spinning fast.
- I wonder: Why does the top stay upright while spinning?
- I think: Because the top is designed with a pointed base and balanced shape, it spins steadily for a long time.

Eraser:
- I observe: The eraser spins for a short time and quickly falls to one side.
- I wonder: Why does the eraser not spin as well as a coin?
- I think: Because the eraser is rectangular and not symmetrical, it loses balance quickly.

Final Answer: Round and symmetrical objects (like coins and tops) spin better and longer. Irregular-shaped objects (like stones and erasers) do not spin well.

Given: We observe how different changes to a spinner affect its spinning.

Concept: A spinner works best when it is balanced and the pivot (toothpick) is exactly at the centre. Shape and balance affect how well and how long a spinner spins.

Completed Table:

Toothpick at the centre:
- What do you observe? Spins
- Any other observations: Spins smoothly and for a longer time because it is balanced.

Toothpick away from the centre:
- What do you observe? Spins, but not well
- Any other observations: Wobbles and falls quickly because it is unbalanced.

A square spinner:
- What do you observe? Spins, but not smoothly
- Any other observations: The corners make it wobble; it does not spin as long as a circular spinner.

Circular spinner with a circular mark on its body:
- What do you observe? Spins
- Any other observations: The circular mark appears to blur or form a pattern when spinning fast; the mark seems to move in a circle.

Any other (e.g., triangular spinner):
- What do you observe? Spins briefly
- Any other observations: Irregular shapes do not spin as smoothly or as long as circular ones.

Final Answer: A circular spinner with the toothpick exactly at the centre spins the best. Balance and shape are key factors for good spinning.

Given: We drop various objects in water and observe whether they float or sink.

Concept: Whether an object floats or sinks depends not only on its weight but also on its shape and the amount of water it displaces. An object floats if it displaces water equal to its own weight.

Completed Table:

Leaf:
- Guess: F (Float) | Reason: It is light
- Observation: F (Float) | Reason: It is light and its flat shape helps it stay on the surface.

Iron nail or pin:
- Guess: S (Sink) | Reason: It is heavy and made of metal
- Observation: S (Sink) | Reason: Iron is denser than water; it sinks despite being small.

Empty steel bowl:
- Guess: S (Sink) | Reason: It is made of metal
- Observation: F (Float) | Reason: The bowl shape traps air inside, making it less dense overall, so it floats.

A piece of stone:
- Guess: S (Sink) | Reason: It is heavy
- Observation: S (Sink) | Reason: Stone is denser than water.

Empty bottle with a closed lid:
- Guess: F (Float) | Reason: It is light and has air inside
- Observation: F (Float) | Reason: The air trapped inside makes it less dense than water.

Bottle full of water with a closed lid:
- Guess: S (Sink) | Reason: It is heavy with water inside
- Observation: S (Sink) | Reason: It is now denser than the surrounding water.

Final Answer: Floating or sinking depends on both the weight and the shape of the object. An empty bowl floats even though it is made of metal, because its shape traps air.

Given: We need to discuss whether weight alone decides if an object floats or sinks.

Concept: Floating and sinking depend on density and shape, not just weight. An object floats if it is less dense than water or if its shape allows it to displace enough water.

Answer:
No, not all light objects float and not all heavy objects sink.

Heavy objects that floated:
- Empty steel bowl — it is made of heavy metal, but its cup shape traps air, so it floats.
- A large ship — made of heavy steel, but floats because of its hollow shape.

Lighter objects that sank:
- A small iron pin or nail — though very light in weight, it is dense and sinks.
- A small pebble — lighter than a bowl but still sinks because it is denser than water.

Conclusion: Floating or sinking of an object cannot be decided based just on whether it is heavy or light. It also depends on the shape of the object and how much water it displaces.

Final Answer: Shape and density are equally important. A heavy steel bowl floats because of its shape, while a tiny iron pin sinks because of its high density.

Given: We test aluminium foil in three different shapes to see if shape affects floating or sinking.

Concept: Shape affects how much water an object displaces. A flat or cup-shaped object displaces more water and can float, while a compact ball shape displaces less water and sinks.

Completed Table:

Spread out:
- Guess: F (Float) | Reason: It is thin and light; the flat shape will rest on water.
- Observation: F (Float) | Reason: The flat shape spreads the weight over a large area and displaces enough water to float.

Pressed tightly into a ball:
- Guess: S (Sink) | Reason: It becomes compact and heavy for its size.
- Observation: S (Sink) | Reason: The ball shape displaces very little water; it is denser than water in that form, so it sinks.

In a cup-like shape:
- Guess: F (Float) | Reason: Like a bowl, it will trap air and float.
- Observation: F (Float) | Reason: The cup shape traps air inside, making it less dense overall, so it floats.

Conclusion: By changing the shape of the same piece of aluminium foil, we can make it float or sink. Shape plays an important role in floating and sinking.

Final Answer: The same aluminium foil floats when spread out or cup-shaped, but sinks when pressed into a tight ball. This proves that shape determines whether an object floats or sinks.

Given: We have made a boat and need to compare it with others and identify its strengths and challenges.

Concept: A good boat should be able to float, carry weight (load), be stable (not tip over easily), and be strong enough not to break.

Sample Completed Table (answers will vary based on the boat made):

Strengths of your boat:
1. It floats well and does not sink easily.
2. It can carry some load (small stones or coins) without tipping.
3. It has a wide, stable base that keeps it balanced.

Challenges of your boat:
1. It tips over when too much weight is placed on one side.
2. Water seeps in slowly through the joints.
3. It is not very strong and may break if pressed.

How to improve: I can make the base wider for better balance, use waterproof tape to seal the joints, and use stronger material to make it more durable.

Final Answer: Every boat design has strengths and weaknesses. We can improve our boat by making it wider, sealing gaps, and using stronger materials.

Given: Ravi observes that a spinning spinner slows down and stops. He wants to ask questions about this.

Concept: Good scientific enquiry involves asking 'why', 'how', and 'what if' questions based on observations.

Two questions Ravi could ask:

1. Why does the spinner slow down and stop on its own?
(Expected understanding: There is a force called friction between the toothpick/base and the surface that slows it down. Air resistance also plays a role.)

2. What can I do to make the spinner spin for a longer time?
(Expected understanding: Using a smoother surface, a sharper tip, or spinning it faster could help it spin longer.)

Bonus questions (optional):
3. Why does the spinner wobble just before it stops?
4. Would the spinner spin longer on a smooth surface than on a rough surface?

Final Answer: Ravi could ask — (1) Why does the spinner slow down and stop? (2) How can I make the spinner spin for a longer time?

Given: A balance or seesaw is bending (tilting) towards side 'A', meaning side A is heavier.

Concept: A balance is level (horizontal) when the weight on both sides is equal. If one side is heavier, it goes down.

To balance it, we can do one or more of the following:

1. Remove some weight from side A — so that both sides become equal.
2. Add more weight to the other side (side B) — to make it equal to side A.
3. Move the weight on side A closer to the centre — this reduces the turning effect (moment of force) on side A.
4. Move the weight on side B farther from the centre — this increases the turning effect on side B.

Final Answer: To balance the figure that is bending towards side A, we should either remove weight from side A or add weight to side B until both sides are equal.

Given: We need to explain how to make a floating object sink and a sinking object float.

Concept: Floating and sinking depend on density and shape. We can change these by adding weight, changing shape, or trapping/removing air.

To make a floating object sink:
1. Add weight to it — for example, attach a heavy stone to a floating bottle; the extra weight will make it sink.
2. Fill it with water — for example, fill an empty floating bottle with water; it will become denser and sink.
3. Change its shape — for example, press a floating aluminium foil into a tight ball; it will sink.

To make a sinking object float:
1. Change its shape — for example, flatten a lump of clay into a bowl shape; it will trap air and float.
2. Attach it to a floating object — for example, tie a stone to a piece of thermocol or wood; the combined object may float.
3. Place it in a container that floats — for example, put a coin inside a floating boat.

Final Answer: A floating object can be made to sink by adding weight or filling it with water. A sinking object can be made to float by changing its shape (like a bowl) or attaching it to something that floats.

Given: A list of objects — Wax, Marble, Thermocol, Candle, Coin, Cork, Leaf, Eraser, Spoon, Ice-cube, Potato, Tomato, Pumpkin, Lemon.

Concept: Objects that are less dense than water float; objects that are denser than water sink. Shape also plays a role.

Classification:

Things that float:
| Object | Reason |
|---|---|
| Wax | Less dense than water |
| Thermocol | Very light; much less dense than water |
| Candle | Less dense than water (wax-based) |
| Cork | Very light and less dense than water |
| Leaf | Light and flat; less dense than water |
| Ice-cube | Ice is slightly less dense than water |
| Tomato | Less dense than water |
| Pumpkin | Less dense than water; large and hollow inside |
| Lemon | Less dense than water |

Things that sink:
| Object | Reason |
|---|---|
| Marble | Denser than water |
| Coin | Metal is denser than water |
| Eraser | Denser than water |
| Spoon | Metal is denser than water |
| Potato | Slightly denser than water |

Note: Some results may vary slightly depending on the size and type of object. For example, a lemon floats when whole (air pockets inside the peel) but may sink when peeled. A potato is very close to the density of water and may barely sink.

Final Answer:
- Float: Wax, Thermocol, Candle, Cork, Leaf, Ice-cube, Tomato, Pumpkin, Lemon
- Sink: Marble, Coin, Eraser, Spoon, Potato