Objects that move with a constant velocity (same speed ... same direction) experience a balance of forces. Oppositely-directed forces are of the same strength. On the other hand, objects that accelerate experience an unbalanced force that is directed in the direction of the object's acceleration.
Change of State - Questions 1 Help
An elevator rider is moving upward at a constant speed. The Force Diagram for this state of motion is shown on the left. What will the Force Diagram look like when this upward-moving rider undergoes a slowing down process? Select a force diagram from the choices provided on the right.
Try one of these links to The Physics Classroom Tutorial for more help:
Balanced vs. Unbalanced Forces
Types of Forces
Drawing Free-Body Diagrams
The Big Misconception