A body is imparted motion from rest to move in a straight line. If it is then obstructed by an opposite force, then

Options

A. the body may necessarily change direction
B. the body is sure to slow donw
C. the body will necessarily continue to move in the same direction at the same speed
D. none of the above

Explanation

To solve the problem, we need to analyze the situation where a body is moving in a straight line and is then subjected to an opposite force. Let's break down the steps:

### Step-by-Step Solution:

1. **Initial Condition**: The body starts from rest and is moving in a straight line. This means its initial velocity \( u = 0 \) and it gains some velocity \( v \) as it moves.

2. **Application of Opposite Force**: An opposite force is applied to the body. This force acts in the direction opposite to the motion of the body. According to Newton's second law, this force will cause a deceleration (or retardation) of the body.

3. **Effect of the Opposite Force**: The application of the opposite force will result in a decrease in the body’s velocity. The body will start to slow down due to this force.

4. **Stopping Condition**: If the opposite force continues to act on the body, it will eventually bring the body to a stop. At this point, the velocity of the body will become zero.

5. **Post-Stop Motion**: After the body comes to rest, if the force continues to act, the body will then start to move in the direction of the force (which is opposite to its initial direction of motion). This means that the body may change direction, but it is not guaranteed that it will change direction immediately or necessarily.

6. **Conclusion**: Based on the analysis:
- The body will definitely slow down due to the opposite force (this confirms option 2).
- The body may change direction after coming to rest, but it is not guaranteed to do so immediately (this makes option 1 uncertain).
- The body will not continue to move in the same direction at the same speed (this negates option 3).
- Therefore, option 4 (none of this) is incorrect.

### Final Answer:
The correct option is that the body is sure to slow down (Option 2).

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