EXTENSION IDEA - Metals: The Best Shot
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An activity based on the shot put for those who like a challenge! In shot put, the shot must be made of a substance that is heavy enough, yet not too big or too small. Density is a measurement of the mass (measured in kilograms or grams) compared to the volume (measured in cubic metres or cubic centimetres). Density = mass/volumeAn object's volume can be worked out by dividing its mass by its density. Volume = mass/density |
Allsport |
Densities of various metals
|
Metal |
|
Mass of the |
Volume of the |
|
Aluminium |
2.7 |
4000 |
|
|
Zinc |
7.1 |
4000 |
|
|
Iron |
7.8 |
4000 |
512 |
|
Copper |
8.9 |
4000 |
|
|
Lead |
11.9 |
4000 |
|
|
Gold |
19.3 |
4000 |
Using your calculator, fill in the table above by working out the volume of the womens' 4kg shot, if it was made from each of the metals listed in the table. The completed example shows that a 4000g shot of iron (density 7.8 g/cm3) is 4000/7.8 cm3 = 512 cm3, the correct size of a shot.
1. Which metals would make shots too big? Why would this be a problem for the athletes?
2. Shots can also be made of brass, an alloy (combination) of copper and zinc. Using the data in the above table, explain why brass would create a shot of similar size to one made of iron?
3. Using copper, lead and gold would make shots smaller than the specified sizes for competitions. However, apart from size, there are also other reasons these metals would be unsuitable.
- Why would copper be unsuitable? (Hint: think of a copper wire – what features does it have?)
- Gold has the same problem, and anyway it would be a silly idea as it would cost a fortune! Why do you think gold is so expensive?
- Why wouldn’t it be a good idea to use lead? (Hint: think about types of petrol. Why do we have unleaded petrol?)