Which of the following is true regarding projectile motion ?

Options

A. Horizontal velocity of projectile is constant.
B. Vertical velocity of projectile is constant.
C. Acceleration is not constant.
D. Momentum is constant.

Explanation

To determine which statement is true regarding projectile motion, we will analyze each option based on the principles of projectile motion.

### Step-by-Step Solution:

1. **Understanding Projectile Motion**:
- A projectile is an object that is thrown into the air with an initial velocity at an angle to the horizontal. The motion can be analyzed in two components: horizontal and vertical.

2. **Analyzing Horizontal Velocity**:
- In projectile motion, there is no horizontal acceleration (assuming air resistance is negligible). Therefore, the horizontal component of velocity remains constant throughout the motion.
- **Conclusion**: The horizontal velocity of the projectile is constant.

3. **Analyzing Vertical Velocity**:
- The vertical component of velocity is affected by gravity. As the projectile rises, the vertical velocity decreases until it reaches its peak (where it becomes zero), and then it increases as it falls back down.
- **Conclusion**: The vertical velocity of the projectile is not constant.

4. **Analyzing Acceleration**:
- The only acceleration acting on the projectile is due to gravity, which is constant (approximately \(9.81 \, m/s^2\) downward).
- **Conclusion**: The acceleration is constant throughout the motion.

5. **Analyzing Momentum**:
- Momentum is defined as the product of mass and velocity. Since the velocity of the projectile changes (due to the changing vertical component), the momentum of the projectile is not constant.
- **Conclusion**: The momentum of the projectile is not constant.

### Final Evaluation of Options:
- **Option 1**: Horizontal velocity of the projectile is constant. **(True)**
- **Option 2**: Vertical velocity of the projectile is constant. **(False)**
- **Option 3**: Acceleration is not constant. **(False)**
- **Option 4**: Momentum is constant. **(False)**

### Answer:
The correct statement regarding projectile motion is **Option 1: The horizontal velocity of the projectile is constant**.

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