What happens when you open a switch?
a. an electric circuit is closed
b. the resistance in the wire is reduced
c. current cannot flow
d. there is a short circuit

Arunner is training for an upcoming marathon by running around a 100-m-diameter circular track at constant speed. let a coordinate system have its origin at the center of the circle with the x-axis pointing east and the y-axis north. the runner starts at (x, y) = (50 m, 0 m) and runs 2.5 times around the track in a clockwise direction.