Which statements can be possible cases in one/two dimensional motion:

Options

A. A body has zero velocity and still be accelerating
B. The velocity of an object reverses direction when acceleration is constant
C. An object be increasing in speed as its acceleration decreases
D. None of these

Answer

To determine which statements can be possible cases in one or two-dimensional motion, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement 1: A body has zero velocity and can still be accelerating.**
- This statement is **true**. For example, consider a stone thrown upwards. At its maximum height, the stone's velocity is zero, but it is still under the influence of gravitational acceleration (which is directed downwards). Thus, it is possible for an object to have zero velocity while still experiencing acceleration.

2. **Statement 2: The velocity of an object can reverse direction when acceleration is constant.**
- This statement is also **true**. For instance, if an object is moving in a positive direction and experiences a constant negative acceleration, it will eventually slow down to zero velocity and then start moving in the negative direction. This means the velocity can reverse while the acceleration remains constant.

3. **Statement 3: An object can be increasing in speed while its acceleration decreases.**
- This statement is **true** as well. For example, if an object is moving with an initial speed of 10 m/s and has an acceleration of 5 m/s², its speed will increase. If the acceleration decreases to 2 m/s², the object will still continue to speed up, albeit at a slower rate. As long as the acceleration remains positive, the speed will continue to increase.

4. **Statement 4: None of these are correct.**
- This statement is **false** because all the previous statements (1, 2, and 3) are correct.

### Conclusion:
All three statements (1, 2, and 3) are possible cases in one or two-dimensional motion. Therefore, the answer is that statements 1, 2, and 3 are correct.