Effect of a retarding force – what does it not do? A retarding (opposing) force acts on a moving body. Identify what a retarding force does not cause.

Introduction / Context:
Forces are classified by the effect they produce on motion. A retarding force specifically opposes the current direction of motion, such as kinetic friction or aerodynamic drag, and thus reduces speed or kinetic energy. Recognizing what a retarding force cannot do sharpens physical intuition for dynamics problems and design scenarios.

Given Data / Assumptions:

• The body is subject to an opposing (retarding) force.
• Other forces may or may not be present, but the question focuses on the inherent effect of the retarding force itself.
• Classical Newtonian framework applies.

Concept / Approach:

A retarding force does negative work on a moving body, reducing its kinetic energy. If no additional driving force exists, the speed decreases and may eventually reach zero. By definition, a retarding force cannot by itself initiate motion of a body initially at rest, because it acts opposite to any would-be motion and cannot supply positive work to start movement.

Step-by-Step Solution:

Verification / Alternative check:

Newton’s second law: ΣF = m * a. With only a retarding force present and the body at rest, the net force does not favor motion initiation in the positive direction; hence a = 0 or negative relative to that direction.

Why Other Options Are Wrong:

(a) and (b) are true descriptions of a retarding force; it changes motion by reducing speed. (d) “none of these” is wrong because one option is correct. (e) Reversing direction would require additional dynamics; a retarding force alone cannot reverse unless other conditions change.

Common Pitfalls:

Confusing cause (force) with outcome under multiple forces; ignoring sign conventions for work and acceleration.

Final Answer:

introduce (initiate) the motion of a body at rest