Pressure in a fluid and the force that pressure produces differ in one important respect. Which statement is correct?
APressure is a vector, force is a scalar
BPressure is a scalar, force is a vector
CBoth pressure and force are scalars
DBoth pressure and force are vectors
Answer & Solution
Correct answer: B. Pressure is a scalar, force is a vector
1. Fluid pressure has no direction of its own, which makes it a scalar quantity.
2. The forces that a pressure produces do have well defined directions, always perpendicular to the surface they act on, which makes them vectors.
3. So pressure is the scalar and force is the vector, and swapping the two reverses the physics.
4. Treating both as scalars would leave the perpendicular direction of the force unexplained.
5. Treating both as vectors would require a pressure to point somewhere, which a swimmer feeling pressure on all sides shows it does not.
_Source: OpenStax College Physics (CC BY 4.0), Ch 11 "Fluid Statics", section 11.3 Pressure_
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