A player throws a ball vertically upwards with velocity u. At highest point,

Options

A. 1. both the velocity and acceleration of the ball are zero.
B. 2. the velocity of the ball is u but its acceleration
C. 3. the velocity of the ball is zero but its acceleration is g.
D. 4. the velocity of the ball is u but its acceleration is g.

Explanation

To solve the problem, we need to analyze the motion of a ball thrown vertically upwards with an initial velocity \( u \). We will determine the conditions at the highest point of its trajectory.

### Step-by-step Solution:

1. **Understanding the Motion**: When a ball is thrown upwards, it moves against the force of gravity. As it ascends, the gravitational force acts downwards, causing the ball to decelerate until it reaches its highest point.

2. **Initial Conditions**:
- Let the initial velocity of the ball be \( u \).
- The acceleration due to gravity \( g \) acts downwards and has a magnitude of \( 9.8 \, \text{m/s}^2 \) (or approximately \( 10 \, \text{m/s}^2 \) for simpler calculations).

3. **At the Highest Point**:
- At the highest point of its trajectory, the ball momentarily comes to rest before it starts descending. Therefore, the velocity \( v \) at this point is \( 0 \, \text{m/s} \).
- However, the acceleration due to gravity \( g \) continues to act on the ball, which means the acceleration is not zero.

4. **Conclusion**:
- **Velocity**: \( v = 0 \, \text{m/s} \) at the highest point.
- **Acceleration**: \( a = g \) (approximately \( 10 \, \text{m/s}^2 \)) acting downwards.

5. **Evaluating the Options**:
- **Option 1**: Both velocity and acceleration of the ball are 0. (Incorrect)
- **Option 2**: The velocity of the ball is \( u \) but its acceleration is not clear. (Incorrect)
- **Option 3**: The velocity of the ball is 0 but its acceleration is \( g \). (Correct)
- **Option 4**: The velocity of the ball is \( u \) but its acceleration is \( g \). (Incorrect)

Thus, the correct answer is **Option 3**.