Which of the following statements is/are correct about work?

Options

A. (a) In a certain reference frame,
`W_("pseudo force")+W_("conservative force")+W_("non-conservative force")+W_("other forces")=DeltaK`
B. (b) Work done by friction is always negative.
C. (c) Work done by a force is defined as the dot product of the force and the displacement of the point of application of force.
D. (d) Work done by conservative force in moving a body from A to B =potential energy of the body at A-potential energy of the body at B.

Explanation

To determine which statements about work are correct, we will analyze each statement one by one based on the principles of physics.

### Step-by-Step Solution:

1. **Statement A**: "In a certain reference frame, work done by pseudo force plus work done by conservative force plus work done by non-conservative force plus work done by other force is equal to change in kinetic energy."
- **Analysis**: According to the work-energy theorem, the total work done by all forces acting on an object is equal to the change in its kinetic energy. This includes work done by pseudo forces, conservative forces, non-conservative forces, and any other forces.
- **Conclusion**: This statement is **correct**.

2. **Statement B**: "Work done by friction is always negative."
- **Analysis**: The work done by friction can be negative (when it opposes motion), positive (in some cases, like when friction acts in the direction of motion), or zero (when there is no displacement). Therefore, it is not accurate to say that it is always negative.
- **Conclusion**: This statement is **incorrect**.

3. **Statement C**: "Work done by force is defined as the product of force and displacement of the point of application of force."
- **Analysis**: The work done (W) by a force (F) acting on an object is defined as the dot product of the force vector and the displacement vector. Mathematically, it is expressed as W = F · s = |F| |s| cos(θ), where θ is the angle between the force and displacement vectors.
- **Conclusion**: This statement is **correct**.

4. **Statement D**: "Work done by conservative force in moving a body from A to B is equal to potential energy of body at A minus potential energy of body at B."
- **Analysis**: The work done by a conservative force when moving an object from one point to another is indeed related to the change in potential energy. Specifically, it can be expressed as W = PE_A - PE_B, where PE_A is the potential energy at point A and PE_B is the potential energy at point B.
- **Conclusion**: This statement is **correct**.

### Final Summary:
- Statement A: Correct
- Statement B: Incorrect
- Statement C: Correct
- Statement D: Correct

Thus, the correct statements about work are A, C, and D.