Forces in Two Dimensions - Mission F2D5 Detailed Help

An object of mass 'm' is placed upon an inclined plane with an incline angle of 'theta.' If frictional forces can be ignored, the force that causes the object to accelerate down the incline is equivalent to ____.


 
What accelerates an object down an inclined plane? Is it friction? Normal force? Gravity force? The accelerating force is the force of gravity. But be careful. Gravity is directed straight down and not in the direction of the net force. It is only the component of the force of gravity that is parallel to the inclined plane that can accelerate an object down the plane. The means of determining its value is described in the Math Magic section.


 
The force of gravity is neither in the direction of the acceleration nor perpendicular to it. The goal is always to have all forces directed perpendicular or parallel to each other and to the acceleration. So it is the habit on inclined plane problems such as this one to resolve the force of gravity into two components - one being parallel to the inclined plane and the other perpendicular to it. The formulas for resolving the force of gravity into its components are:
 
Fparallel= m • g • sine(Θ) 

Fperpendicular= m • g • cosine(Θ)