A small ball attached to the end of a string experiences a uniform circular motion on a horizontal frictionless table. In order to keep the ball moving
in a circle, the string must apply force on the ball toward the center of the
circle. Which of the following refers to a reaction force?

Complete these sentences. if a roller coaster train has a potential energy of 1,500 j and a kinetic energy of 500 j as it starts to travel downhill, its total energy isj. once the roller coaster train gets closer to the bottom of the hill, its kinetic energy increases to 1,100 j, and its potential energy decreases to j. when the train reaches the bottom of the track and is traveling along the ground, its kinetic energy isj.