In which situation is the object experiencing balanced forces? a) a girl swings on a swing at the playground. b) a car brakes as it approaches a traffic light. c) a sled speeds up as it slides down a snow-covered hill. d) a sky diver reaches terminal velocity when he stops accelerating.

D) A sky diver reaches terminal velocity when he stops accelerating.
F = mass*gravity = Force of air resistance pushing up on the person
Reached terminal velocity = acceleration = zero 

Answer;

D) A sky diver reaches terminal velocity when he stops accelerating.

Explanation;Balanced forces are forces that act in opposite directions and are equal in size. When an object is acted upon by unbalanced forces then the object stays still or at rest or continues moving at a constant velocity in the same direction.Unbalanced forces cause an object or a body to change its motion or velocity and direction.A sky diver who reaches terminal velocity when he stops accelerating, experiences balanced forces. Terminal velocity being a point at which the drag force is equal to the force of gravity.