motion (1) if all air resistance were removed,

the surface were perfectly level.

second law states that an imbalance of force on

a body tends to produce an acceleration in the

direction of the force. The acceleration, if any,

is directly proportional to the force. It is inversely

proportional to the mass of the body. This law

can be explained by throwing a common softball.

The force required to accelerate the ball to a rate

2

of 50 ft/sec would have to be doubled to obtain

2

an acceleration rate of 100 ft/sec . However, if

the mass of the ball were doubled, the original

acceleration rate would be cut in half. You would

2

2

have 50 ft/sec reduced to 25 ft/sec .

law states that for every action there is an equal

and opposite reaction. You have demonstrated

this law if you have ever jumped from a boat up

to a dock or a beach. The boat moved opposite

to the direction you jumped. The recoil from

firing a shotgun is another example of action-

reaction. Figure 4-10 depicts these examples.

In an airplane, the greater the mass of air

handled by the engine, the more it is accelerated

by the engine. The force built up to thrust the

plane forward is also greater. In a gas turbine,

the thrust velocity can be absorbed by the turbine

rotor and converted to mechanical energy. This

is done by adding more and progressively larger

power turbine wheels.

factors concerning noncompressible fluids.

Consider the system shown in figure 4-11.

Chamber A is under pressure and is connected

Blaise Pascal was a French philosopher and

by a tube to chamber B, which is also under

mathematician who lived from 1623 to 1662 A.D.

pressure. Chamber A is under static pressure

His work, simply stated, could be interpreted as

of 100 psi. The pressure at some point, X,

pressure exerted at any point upon an enclosed

along the connecting tube consists of a velocity

liquid is transmitted undiminished in all

pressure of 10 psi. This is exerted in a direction

directions.

parallel to the line of flow. Added is the

Pascal's law governs the BEHAVIOR of the

unused static pressure of 90 psi, which obeys

static factors concerning noncompressible fluids

Pascal's law and operates equally in all directions.

when taken by themselves.

As the fluid enters chamber B from the

constricted space, it is slowed down. In so

doing, its velocity head is changed back to

pressure head. The force required to absorb

Jacques (or Jakob) Bernoulli was a Swiss

the fluid's inertia equals the force required to

philosopher and mathematician who lived

start the fluid moving originally. Therefore, the

from 1654 to 1705 A.D. He worked extensively

static pressure in chamber B is again equal to

with hydraulics and the pressure-temperature

that in chamber A. It was lower at intermediate

relationship. Bernoulli's principle governs the

point X.

RELATIONSHIP of the static and dynamic

4-10

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