How much force acts on a body whose momentum is constant

Options

A. zero
B. `p//2t`
C. `2p//t`
D. none of these

Explanation

To solve the question, "How much force acts on a body whose momentum is constant?", we can follow these steps:

### Step 1: Understand the Concept of Momentum
Momentum (p) is defined as the product of mass (m) and velocity (v) of an object. Mathematically, it is expressed as:
\[ p = m \cdot v \]
When we say that momentum is constant, it means that neither the magnitude of the momentum nor its direction is changing.

### Step 2: Apply Newton's Second Law of Motion
According to Newton's second law, the net external force (F) acting on an object is equal to the rate of change of momentum (p) with respect to time (t):
\[ F = \frac{dp}{dt} \]
Where \( \frac{dp}{dt} \) is the derivative of momentum with respect to time.

### Step 3: Analyze the Given Condition
Since the problem states that the momentum is constant, we can conclude that:
\[ \frac{dp}{dt} = 0 \]
This means that the rate of change of momentum is zero because the momentum does not change over time.

### Step 4: Calculate the Force
Substituting the value of \( \frac{dp}{dt} \) into the equation from Step 2:
\[ F = 0 \]
This indicates that the net external force acting on the body is zero.

### Step 5: Conclusion
Thus, the answer to the question is that the force acting on a body whose momentum is constant is:
\[ \text{Force} = 0 \]

### Final Answer
The correct option is that the force acting on the body is zero.

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