Fluid

Question 1

What happens when you apply a force onto a fluid?

Answer 1

Apply a force (usually through an applied pressure) to a fluid and it changes its shape. Remove the force and IT DOES NOT regain anything like its original shape

Question 2

What is hydrostatics?

Answer 2

No fluid Motion and the fluid is usually a liquid

Question 3

What is the flow rate, mass conservation, momentum and forces?

Answer 3

Characterise flow by its flow rate; consider the implications of mass conservation for flows, consider the relationship between fluid momentum and forces – the application of Newton’s second law for fluids.

Question 4

What is the Bernoulli equation of fluid mechanism?

Answer 4

Energy and its conservation in fluid flows

Question 5

What are fluids? (2)

Answer 5

The fluids that we will study in this unit are assumed to be incompressible (they have constant density, ρ) and behave inviscidly, that is they slide freely over a solid surface.

Question 6

What is hydrostatic pressure in a fluid? (2)

Answer 6

The force due to the weight of the fluid above the plate

Pressure acts perpendicular to a boundary
and can even generate an upward force.

Question 7

Work is done when a force acts_________

Answer 7

Work is done when a force acts through any displacement, not perpendicular to the line of action of the force

Question 8

Explain what a conservative force is. Are gravitational and elastic forces conservative?

Answer 8

When the work done by a force moving between A and B is independent of the path taken, the force is a conservative force

Weight and elastic (eg. spring) forces are conservative

Question 9

Power is a measure of the rate at which __________

Answer 9

Power is a measure of the rate at which work is done

Question 10

Is it correct to say that all of our kinetics methods (Newton II, Impulse-Momentum and
∑ Energy methods) are derived from the empirical law, F = ma ?

Answer 10

Yes

Question 11

Describe in words the meaning of “impulse”.

Answer 11

Geometrically, it is the area under the F-t curve,

Question 12

Under what conditions does the conservation of linear momentum apply?

Answer 12

When the particle, or system of particles, is not subjected to any external impulse

Question 13

Is an Earth orbiting satellite “weightless”?

Answer 13

No, being in the earth’s gravitational filed, it experiences a gravitational attraction. If it did not have an appropriate tangential velocity, it would fall to Earth.

Question 14

Describe in words how a n-t coordinate system is aligned in relation to the particle’s motion

Answer 14

The tangential direction is aligned with the particle’s velocity vector (ie. along the path). The normal coordinate is perpendicular to the tangential direction, directed towards the centre of curvature

Question 15

In what sense is the normal coordinate directed?

Answer 15

Towards the centre of curvature

Question 16

Define centripetal acceleration

Answer 16

The component of acceleration directed towards the centre of curvature.

Question 17

What are internal forces found within a structural member?

Answer 17

Forces and moments are transferred along structural members and generate internal stresses (ie. forces distributed over cross sectional areas - not necessarily evenly, sometimes in a quite complicated fashions). Resultants of these distributed forces on any cross-section or “cutting plane” are called “internal forces”.

Question 18

What is a normal force?

Answer 18

The stress distributed over a cross-section may be replaced with a resultant force plus a moment. The component of the resultant force perpendicular to the cross-section is called the Normal forces.

Question 19

What is a shear force?

Answer 19

The component of the resultant force parallel to the cross-section is called the shear force.

Question 20

What is the bending moment?

Answer 20

The stress distributed over a cross-section may be replaced with a resultant force plus a moment, the bending moment is the moment.