A : The direction of velocity of an object can be reversed with constant acceleration.
R : A ball projected upward reverse its direction under the effect of gravity.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statement, then mark (4).

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that "The direction of velocity of an object can be reversed with constant acceleration."
- This is indeed true. When an object is subjected to constant acceleration in the opposite direction of its velocity, it can slow down, stop, and then start moving in the opposite direction.

**Hint**: Think about how acceleration affects velocity. If acceleration is opposite to velocity, it can reduce the speed to zero and then reverse the direction.

2. **Understanding the Reason (R)**:
- The reason states that "A ball projected upward reverses its direction under the effect of gravity."
- When a ball is thrown upwards, it moves against the force of gravity, which acts downwards. The acceleration due to gravity (g) is constant and acts in the opposite direction to the initial velocity of the ball. As the ball rises, its velocity decreases until it reaches the highest point (where velocity is zero), and then it starts to fall back down, thus reversing its direction.

**Hint**: Recall the motion of a projectile. The upward motion is slowed down by gravity until it stops and then falls back down.

3. **Conclusion**:
- Both the assertion (A) and the reason (R) are correct. The assertion correctly describes a scenario where constant acceleration can reverse the direction of velocity, and the reason provides a specific example of this phenomenon (the ball projected upward).
- However, while both statements are true, the reason does not directly explain the assertion in a general sense, as it is just one example of many possible scenarios.

**Final Answer**: Both A and R are correct, but R is not the correct explanation for A. Therefore, the answer is option 2.