We are aware of how our bodies move and are used to people and things moving around us all the time. This means that we have an idea of movement. When we look at a painting or photograph that is not animated, we imagine action, based on what we know about how the world operates.
For example, when you see a photograph of someone you are familiar with smiling in a way that you know, you can almost hear their words and anticipate what they might do or say next.
When you see a photograph of someone mid-air, leaping, you know that gravity will pull them down, and you can imagine the way they will land.
Even though the photographic frame and the subject is not moving, you may still assume or imagine action. This is especially the case in long exposure and action photography.
You don’t need to hear the audio to know that a sound is produced when the mallets strike the xylophone. Your imagination can hear it already. But you might not imagine sound if the mallets were not shown in movement.
From the position of the motorcyclists, you can imagine the riders are traveling with speed around curves. If you have ever watched a race, you might imagine the bikes’ sounds, even though you cannot see movement or hear audio in this image.
This is how still images convey movement. However, it also connects with the viewer’s experience. For example, if you have never heard or seen a xylophone before, it might be harder to imagine what is happening.
The above are overt examples. Action can also be conveyed subtly through camera movement and brush strokes, like in the image below.
Here your memory and experience would fill the blanks to give you a sense of what is happening in the image.