Question

In hydrostatics, what would be the summation of the net forces acting on a fluid element?
1. Zero
2. One
3. Less than zero
4. Greater than zero

Answer 1

Correct Answer - Option 1 : Zero

Explanation:

Fluid said is to be in static condition only if,

1. the fluid is at rest i.e. no relative motion between adjacent fluid layers
2. the fluid is flowing ideally i.e. shear stress will be equal to zero
3. the fluid is in rigid motion i.e. constant acceleration

∴ Only forces that are acting on the fluid particles are as follows:

1. Pressure force due to the pressure exerted by fluid particles normal to the surface
2. Gravity force due to self-weight of the particle

For a fluid at rest or for hydrostatic conditions, the summation of the forces acting on the element must be balanced by the gravity force. Hence the summation of the net forces acting on a fluid element is zero.