Acceleration of a particle under projectile motion at the highest point of its trajectory is :

Options

A. `g`
B. zero
C. less than g
D. dependent upon projection velocity

Explanation

To solve the question regarding the acceleration of a particle under projectile motion at the highest point of its trajectory, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Projectile Motion**:
- Projectile motion involves an object being thrown into the air, following a curved path (a parabola) under the influence of gravity.

2. **Identify the Highest Point**:
- At the highest point of the trajectory, the vertical component of the velocity becomes zero. However, the object still has a horizontal component of velocity.

3. **Acceleration in Projectile Motion**:
- In projectile motion, there are two components of motion: horizontal and vertical.
- The horizontal motion has no acceleration (assuming no air resistance), so the horizontal acceleration is zero.
- The vertical motion is affected by gravity, which acts downwards with a constant acceleration of \( g \) (approximately \( 9.81 \, \text{m/s}^2 \)).

4. **Acceleration at the Highest Point**:
- At the highest point, even though the vertical velocity is zero, the acceleration due to gravity is still acting on the projectile.
- Therefore, the acceleration of the particle at the highest point is \( g \) directed downward.

5. **Conclusion**:
- The acceleration of a particle under projectile motion at the highest point of its trajectory is \( g \) (downward).

### Final Answer:
The acceleration of a particle under projectile motion at the highest point of its trajectory is \( g \) (downward).

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