Which of the following statements is true?

Options

A. The north pole of a magnet attracts south pole of another magnet.
B. Atmospheric pressure is the mass of air in a column of unit area.
C. Pressure = Force/Area of surface, here force acts parallel to the surface on which pressure is to be computed.
D. The electrostatic force comes into play when bodies are in contact only.

Explanation

To determine which of the given statements is true, let's analyze each statement one by one.

### Step 1: Analyze Statement 1
**Statement 1:** The north pole of a magnet attracts the south pole of another magnet.

- This statement is **true**. In magnetism, opposite poles attract each other. Therefore, a north pole will attract a south pole.

### Step 2: Analyze Statement 2
**Statement 2:** Atmospheric pressure is the mass of air in a column of unit area.

- This statement is **false**. Atmospheric pressure is defined as the force exerted by the weight of air above a unit area, not just the mass of air.

### Step 3: Analyze Statement 3
**Statement 3:** Pressure equals force upon area of a surface. Here, force acts parallel to the surface on which pressure is to be computed.

- This statement is **false**. While the formula for pressure (P = F/A) is correct, the force must act **perpendicular** to the surface for the pressure to be correctly calculated. If the force acts parallel to the surface, it does not contribute to the pressure exerted on that surface.

### Step 4: Analyze Statement 4
**Statement 4:** The electrostatic force comes into play when bodies are in contact only.

- This statement is **false**. Electrostatic forces can act at a distance and do not require physical contact between charged bodies. Charged objects can exert forces on each other even when they are not in contact.

### Conclusion
After analyzing all the statements:
- **Statement 1 is true.**
- **Statements 2, 3, and 4 are false.**

Thus, the correct answer is that **Statement 1 is true**.

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