What causes turbulence? a. exposure to ultraviolet rays
b. being too high in the atmosphere
c. severe weather in the troposphere
d. unusually high ocean temperatures

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.