Frictional force between two bodies

Options

A. Adds the motion between the bodies
B. Destroys the motion between the bodies
C. Sometimes helps and sometimes opposes the motion
D. Increases the relative velocity between the bodies

Answer

To solve the question regarding the frictional force between two bodies, we will analyze the scenarios where friction can either assist or oppose motion.

### Step 1: Understanding Friction
Friction is a force that opposes the relative motion between two surfaces in contact. It can act in different directions depending on the situation.

### Step 2: Analyzing the First Scenario (Inclined Plane)
- Consider a ball rolling down an inclined plane.
- In this case, the frictional force acts in the direction of the ball's motion (down the incline).
- Here, friction helps the motion of the ball by preventing it from slipping.

### Step 3: Analyzing the Second Scenario (Rough Surface)
- Now consider a block moving on a rough surface with an applied force \( F \) in a certain direction.
- The frictional force acts in the opposite direction to the applied force \( F \).
- In this scenario, friction opposes the motion of the block.

### Step 4: Conclusion
From the two scenarios analyzed, we can conclude that:
- Friction can either assist or oppose the motion depending on the context.
- Therefore, the correct option is that frictional force between two bodies can sometimes help and sometimes oppose the motion.

### Final Answer
The correct answer is that the frictional force between two bodies can either assist or oppose the motion.

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