Which one among the following statements is correct?
- A.Pressure has magnitude as well as direction
- B.As we go deeper in a liquid, the pressure decreases
- C.Action and reaction forces act on the same object
- D.Pascal and N/m² represent the same unit
Correct answer
Explanation
The correct answer is D, Pascal and N/m² represent the same unit. One pascal is defined as a force of one newton acting on an area of one square metre.
Pressure is force per unit area, and its SI unit, named after the French scientist Blaise Pascal, is the pascal (Pa): 1 Pa = 1 N/m². Larger values are given in kilopascals, and atmospheric pressure at sea level is about 1.013 × 10⁵ Pa. Pressure at a point in a fluid acts equally in all directions, which is why it is treated as a scalar quantity.
A is wrong: pressure has only magnitude; it is a scalar, while the force that causes it is a vector.
B is wrong: pressure in a liquid increases with depth, as p = hρg, which is why the walls of a dam are made thicker at the base.
C is wrong: by Newton's third law, action and reaction act on two different objects, so they never cancel each other.
Exam tip: 1 Pa = 1 N/m²; liquid pressure rises with depth (hρg); action and reaction act on different bodies.
Practice Questions
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