WTMA Hydraulics and Fluid Dynamics 5

Question 1

A hydraulic system uses oil with a specific gravity of 0.9. Compared to water, the oil weighs:

Accepted Answer

10% less per unit volume

Answer

Specific gravity of 0.9 means the oil is 90% as dense as water, so it weighs 10% less per unit volume.

Question 2

In a hydraulic system, what is 'back pressure'?

Accepted Answer

Residual pressure on the return side of an actuator opposing its motion

Answer

Back pressure is the pressure that exists in the return line and acts against the moving side of a cylinder, reducing net force.

Question 3

A check valve is installed in a hydraulic line. What does it do?

Accepted Answer

Allows fluid to flow in one direction only

Answer

A check valve contains a ball or poppet that blocks reverse flow while allowing free flow in the intended direction.

Question 4

When a hydraulic hose bursts suddenly, the most immediate danger is:

Accepted Answer

High-pressure fluid injection through skin, which can cause severe injury

Answer

High-pressure fluid can penetrate skin and cause serious internal injury even through small pinhole leaks.

Question 5

A hydraulic motor converts:

Accepted Answer

Fluid pressure and flow into rotational mechanical output

Answer

A hydraulic motor is the reverse of a pump — pressurized fluid enters and drives a shaft to rotate.

WTMA - Wiesen Test of Mechanical Aptitude Practice Test