We cannot feel speed. But our senses let us know that we are moving. We see things (1) past us, and feel that we are being (2) . We can feel acceleration, an increase in speed. But we notice it for only a short time. For instance, we feel it during the take-off run of an airliner. We feel the plane’s acceleration because our bodies don’t gain speed (3) the plane does. It seems that something is pushing us back (4) the seat. Actually, our bodies are trying to stay in the same place while the plane is carrying us forward. Soon the plane (5) a steady speed. Then, because there is (6) any change in speed, the feeling of forward motion stops.