The force required to overcome friction at the instant an object starts moving from rest is a measure of :

Options

A. Rolling friction
B. Sliding friction
C. Drag
D. Static friction

Explanation

To solve the question, "The force required to overcome friction at the instant an object starts moving from rest is a measure of:", we need to analyze the types of friction and understand the context of the problem.

### Step-by-Step Solution:

1. **Understand the Concept of Friction**:
- Friction is a force that opposes the relative motion of two surfaces in contact. There are different types of friction, including static friction, sliding friction, rolling friction, and drag.

2. **Identify the Scenario**:
- The question specifically mentions an object that is at rest and requires a force to start moving. This indicates that we are dealing with the initial resistance to motion.

3. **Define Static Friction**:
- Static friction is the frictional force that must be overcome to start moving an object that is at rest. It acts on an object that is not moving and prevents it from starting to move.

4. **Recognize Other Types of Friction**:
- Sliding friction occurs when an object is already in motion and sliding over a surface.
- Rolling friction occurs when an object rolls over a surface.
- Drag is the resistance experienced by an object moving through a fluid (like air or water).

5. **Conclusion**:
- Since the question asks about the force required to overcome friction at the moment an object starts moving from rest, the correct answer is static friction.

### Final Answer:
The force required to overcome friction at the instant an object starts moving from rest is a measure of **static friction**.

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