Final answer:
A public good is nonexcludable and non-rival in consumption. Examples include public radio, which is nonrivalrous, and laptops, which are rivalrous. The free-rider problem occurs when individuals enjoy the benefits of a public good without contributing financially.
Step-by-step explanation:
A public good is a good that is both nonexcludable and non-rival in consumption. Nonexcludable means that it is costly or impossible to exclude others from using the good. Non-rival means that one person's use of the good does not diminish its availability for others.
For example, public radio can be heard by anyone with a radio, so many people can listen at the same time, making it nonrivalrous in consumption. On the other hand, two people cannot use one laptop at the same time, so laptops are rivalrous in consumption.
The free-rider problem arises when a public good is nonexcludable, meaning that individuals can enjoy the benefits of the good without paying for it. This leads to a situation where individuals may choose not to contribute financially to the provision of the public good, relying on others to do so instead.