There are moral obligations, financial obligations, social obligations, professional obligations, and many other kinds.
A person can take on a voluntary commitment, and then it becomes an obligation to fulfill. For example, suppose you offered to take a housebound patient to a medical appointment, or accepted a service position in a volunteer-run organization, or agreed to help out at a charity fund-raiser. Once you’ve pledged your participation, you have an obligation to follow through.
I volunteered to serve as treasurer for a group I belong to. That meant I was obligated to show up at every meeting, collect donations, keep records, make reports, and pay bills. No one forced me to volunteer or to perform the appropriate duties, but I was nevertheless under a degree of compulsion to provide the expected services for the duration of my term.
That sort of thing is aside from obvious obligations such as those that come with supporting a household, raising children, holding a job, etc.
Or perhaps we don’t understand what you mean by “force.”