Final answer:
The component that does not contribute to downward motion on a slope is the perpendicular component of the weight, which balances with the normal force to result in no motion perpendicular to the slope.
Step-by-step explanation:
The component that will not contribute to downward motion on a slope is the perpendicular component of the weight, often represented as N or the normal force. This is because this component is equal in magnitude to the component of the weight perpendicular to the slope (labeled W₁ or w₁ in figures), resulting in no net motion in the perpendicular direction to the slope. This concept is critical to understand when analyzing motion on inclined planes and applying Newton's second law. For an object to slide down an inclined plane at constant velocity, the component of the weight along the slope must be equal to the magnitude of the frictional force opposing the motion.