What happens when the diaphragm contracts?
a. the rib cage moves down.
b. the volume of the thoracic cavity increases.
c. the diaphragm rises.
d. the volume of the thoracic cavity decreases.

Johnny rode his bike to a friend's house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was not able to play. what was his displacement for the total bike ride? how did you determine this? what could we use as a reference point to determine he was in motion during his bike ride? why can you use it as a reference point