Assertion: skateboarder's foot | /r/HasProperty | shown by red and blue arrows
Facets:
Source sentences:
text: They need to provide a changing force to move the board correctly (so that the combined force of gravity and the skater's feet add up to the green arrows above), and they need to provide different amounts of force with each foot (shown by the red and blue arrows above) to steer and turn the board into the right orientation.