Question

Assertion (A): When an object or body is moving at a constant velocity, with no changes in speed or direction, it is dynamic equilibrium.
Reason (R): A cyclist in motion or the body position maintained by a sprinter on the track while running are examples of dynamic equilibrium.

• A. Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

Dynamic Equilibrium requires two things: the object must be moving, and its velocity must be constant (meaning no acceleration or changes in direction).

Answer 1

The Correct Option is A

Step 1: Evaluating Assertion (A):
Equilibrium is divided into static (at rest) and dynamic (in motion). Dynamic equilibrium occurs when an object is in motion with a constant velocity vector, meaning the net external force ($\sum \vec{F} = 0$) and net torque acting on it are zero. Thus, Assertion (A) is True.

Step 2: Evaluating Reason (R):
A cyclist maintaining a steady speed in a straight line or a sprinter running smoothly at peak velocity are classic real-world examples of dynamic equilibrium, where forces like propulsion balance out air resistance and friction. Thus, Reason (R) is True.

Step 3: Assessing the Logical Link:
The reason provides specific examples that illustrate the definition given in the assertion. Because these examples directly apply the principle of constant velocity motion under balanced forces, (R) serves as a correct explanation for (A).