# on deadlines and priority: a physical analogue

Looking at my to-do list today, I noticed for the millionth time how two key attributes of a task seem to be either redundant or in conflict: its due date and its priority.

It always seemed to me that you should only need to assign one or the other. If you have a deadline, then what does the priority affect? If the item is high enough priority, isn’t the due date ASAP?

Today, though, I had a flash of insight. The due date defines how much I have to work on the item in order to get it done in time, almost like the velocity of the task. The priority, however, defines how resistant the job is to being derailed by other tasks, more like the inertia or mass of the task.

Put that way, the two values aren’t redundant at all. In fact, you can put them together to determine the overall momentum of a project, based on the combination of the deadline-driven velocity and the priority-based mass. It might even be possible to come up with a formula for determining the outcome of a collision between two tasks, but I’ll leave that as an exercise for the project manager.