What it shows
Every object has a balance point, the centre of gravity, where its weight seems to act. In sports equipment it is not at the middle, and where it lies changes how the object feels in the hand.
The science
If an object is supported at its centre of gravity, the turning effects of weight on both sides cancel, and it stays level. A bat has more mass toward the blade, so the balance point is nearer the blade end. A bat with the balance point lower down feels heavy to swing but hits with more force.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A cricket bat or a wooden stick
- A hockey stick or a long broom handle
- Two smooth pencils or a sharp-edged ruler
- A thread and a nut for a plumb line
- A metre ruler and chalk
- A notebook
Safety
For this project: Rest equipment on a table and keep your fingers clear when sliding it. Do not swing bats indoors.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Rest the bat on the two index fingers held wide apart, with the bat horizontal.
Slowly slide both fingers toward each other, so they move in turn.
Stop when the fingers meet; the bat is balanced over them. Mark that spot with chalk.
Measure the distance from the handle end to the balance point.
Repeat for the hockey stick and the broom handle.
Express each balance point as a percentage of the full length.
Hang the bat from a nail at the balance point and check that it stays level.
Draw each object to scale and mark its balance point with a dot.
What you should see
The balance point of an even broom handle is at the middle, while the bat and hockey stick balance closer to the heavy end.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What is the centre of gravity?
The point where the whole weight of the object seems to act.
2Why does the finger trick work?
The finger nearer the balance point carries more weight and gets more friction, so the other one slides first.
3Why is the bat’s point nearer the blade?
Most of its mass is in the blade.
4Why does this matter to a player?
It affects how heavy the bat feels and how it swings.
Take it further
Tape a small weight near the handle and then near the tip, and see how the balance point moves.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
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