Forces in Two Dimensions - Mission F2D5 Detailed Help

An object upon an inclined plane is accelerating down the incline. Friction is absent. Which one of the following diagrams represent the free-body diagram for such an object?

Often times, success in physics demands that you have the proper approach - a good game plan. A good game plan for this question would include:
  • Knowing the different types of forces (Fgrav, Fnorm, Fapp, Ffrict, Fair, Ftens, Fspring, etc.) and when they exist, identify which are acting upon the object. Use the Hot Link section if necessary.
  • For each force that acts upon the object, use your understanding of that force type to identify the direction in which it acts.
  • Inspect each choice individually to determine which diagram shows the proper forces in the proper direction.

The force of gravity is always directed straight down. Yet, it is the habit on inclined plane problems to resolve the force of gravity into two components - one being parallel to the inclined plane and the other perpendicular to the incline. But don't be fooled! These parallel and perpendicular components are simply parts of the gravity force. Don't be fooled into looking for forces that are directed in the direction of the components of the gravity force.