If kinetic energy of a body is increasing then.

Options

A. work done by conservative forces must be positive.
B. work done by conservative forces may be positive.
C. work done by conservative forces may be zero
D. work done by non-conservative forces may be zero

Answer

To solve the question, "If kinetic energy of a body is increasing then," we can follow these steps:

### Step 1: Understand the relationship between work and kinetic energy
According to the work-energy theorem, the work done on an object is equal to the change in its kinetic energy. This can be expressed mathematically as:
\[ W = \Delta KE \]
where \( W \) is the work done, and \( \Delta KE \) is the change in kinetic energy.

### Step 2: Define the change in kinetic energy
The change in kinetic energy can be defined as:
\[ \Delta KE = KE_{final} - KE_{initial} \]
If the kinetic energy of the body is increasing, it means:
\[ KE_{final} > KE_{initial} \]
Thus, \( \Delta KE > 0 \).

### Step 3: Relate work done to the change in kinetic energy
Since we established that \( \Delta KE > 0 \), we can conclude that:
\[ W = \Delta KE > 0 \]
This indicates that the work done on the body is positive.

### Step 4: Consider the types of forces involved
- **Conservative Forces**: The work done by conservative forces (like gravity) in a closed path is zero. However, if kinetic energy is increasing, the work done by conservative forces could still be positive if the path is not closed.
- **Non-Conservative Forces**: Non-conservative forces (like friction or applied forces) can do work that changes the kinetic energy of the body. The work done by non-conservative forces can be positive, negative, or zero.

### Step 5: Conclusion
Since the kinetic energy is increasing, the work done must be positive. Therefore, we can conclude that:
- The work done by conservative forces may be positive or zero.
- The work done by non-conservative forces may also be positive or zero.

Thus, the correct answer to the question is that the work done by non-conservative forces may be zero.

### Final Answer
If the kinetic energy of a body is increasing, then the work done by non-conservative forces may be zero.

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