Question

A couple consists of

• A. Two like parallel forces of same magnitude
• B. Two like parallel forces of different magnitudes.
• C. Two unlike parallel forces of same magnitude
• D. Two unlike parallel forces of different magnitudes

Hint:

The net force of a couple is always zero:
\[ \sum F = F - F = 0 \] This ensures that a couple causes only rotation, with absolutely no translation.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
A couple is a system of forces that creates a pure rotational moment without causing any linear translation.

Step 3: Detailed Explanation:
For a set of forces to produce a pure moment (torque) with zero net resultant force:
1. The forces must have the same magnitude (\(F_1 = F_2 = F\)).
2. They must act in opposite directions (unlike parallel forces).
3. They must be separated by a non-zero perpendicular distance (so they do not lie on the same straight line of action).
If they were like parallel forces, their net sum would not be zero, resulting in a net translational force.
Hence, a couple consists of two unlike parallel forces of the same magnitude.

Step 4: Final Answer:
The correct option is 3, which corresponds to "Two unlike parallel forces of same magnitude".