Final answer:
In magnetism experiments, paper clips are commonly used because they can become magnetised and demonstrate the principles of magnetism effectively. Other objects like coins or rocks may not interact with magnets if they're not made of ferromagnetic materials.
Step-by-step explanation:
In the investigation regarding magnets and how they can move objects, the objects commonly used for experimentation include paper clips, as they are typically made of steel, which contains iron. This makes them susceptible to magnetism. For instance, when you use a magnet and rub it along a paper clip, the paper clip can become magnetized and will then be able to attract other paper clips. This experiment helps demonstrate the magnetic properties of certain materials and allows students to observe magnetic force in action. Other objects that might not show magnetic properties when tested, like coins, small rocks, and toy cars, could be made of materials that do not interact with magnets in the same way.