200
In outer space, a small ball of rock and ice travels for thousands of years. Its motion does not change in any way during that time. As it approaches the solar system, however, it comes under the influence of the Sun's gravity and its motion begins to change. Which principle does this demonstrate?
a. Every action has an equal and opposite reaction.
b. An object in motion moves in a straight line at a constant speed until acted on by a net force.
c. Matter may change form but not be created or destroyed.
d. In nature, favorable traits tend to aid in survival and reproduction.
What is b. An object in motion moves in a straight line at a constant speed until acted on by a net force. ?