(a) There are two vertical forces acting on the box, its weight and the restoring force of the spring. What law determines the relationship between these forces when the acceleration of the box is zero?

Newton's first law

Explanation:

-An object will remain at or in uniform motion in a straight line unless acted upon by an external force.

-The acceleration of the box is equal to zero, so the net force on the box should be zero, so:

the total distance that martina travels that day is

(distance from home to mom's office) plus (distance from mom's office to school)

plus (distance from school to library) plus (distance from library to friend's house)

plus (distance from friend's house to martina's house).

(we don't know what any of these distance actually is.)