The statement that best describes the relationship between a baseball's potential and kinetic energy after it is thrown is: Potential energy decreases as kinetic energy increases.
When a baseball is thrown, its kinetic energy increases due to its motion, while its potential energy decreases unless it is thrown upwards or at an angle where height changes come into play. If the ball travels in a straight line and does not gain height, we primarily see an increase in kinetic energy and a decrease in potential energy.