Which explains why a gas does not have a fixed shape?
select one:
a. the particles have very high speeds.
b. the particles are not compressible.
c. the particles are charged.
d. the particles vibrate.

Which of the following situations is impossible? a) an object has velocity directed east and acceleration directed east. b) an object has zero velocity but non-zero acceleration. c) an object has constant non-zero velocity and changing acceleration. d) an object has velocity directed east and acceleration directed west. e) an object has constant non-zero acceleration and changing velocity.