Instruments and Measurements T1-T3

What are the two main types of fluids?

Liquid and gases.

How do liquids and gases differ in terms of compressibility?

Liquids are almost incompressible, while gases are readily compressible.

What is the formula for weight?

W = mg (mass x gravitational acceleration)

What is the gravitational acceleration?

9.81m/s2

Define accurate.

How close a measurement is to the correct value.

Define precise.

How close the agreement is between repeated measurements which are repeated under the same condition.

What are random errors caused by?

Inconsistent measurement, environmental factors, limitations of instruments

What is a random error?

It cannot be predicted, they are unavoidable. They cause measurement values to differ randomly from true value.

How to minimise random errors?

It can be minimised by taking large number of readings and average them. Outlier results should be removed.

What are systematic errors?

They are not random but constant error. It may cause reading to be inconsistently overestimated or underestimated. It cannot be reduced by averaging. Can eliminate error if source of error is known.

What is a parallax error?

It is an error in measured values due to failure to properly align the eye with part of scale you are reading.

How to avoid parallax error?

Position eye directly above the point where you are measuring. Length scale should be in direct contact with object to be measured, not above it.

What is calibration?

Regularly checking an instrument for accuracy by using instrument to take measurements of known value.

How to leave numbers when doing multiplication or division?

follow the LOWEST significant figure.

How to leave numbers when doing addition or subtraction?

follow the LEAST amount of decimal places.

What is specific gravity?

S.G = Density of substance/Density of water or reference

What is a vacuum?

A space with pressure less than atmospheric pressure.

What does a barometer measure?

Atmospheric pressure.

How does a simple U-tube manometer work?

It measures pressure by the height difference of a fluid column.

What is the purpose of an inclined manometer?

To measure small pressure differences more accurately.

State Archimedes’ Principle.

The buoyant force equals the weight of the fluid displaced by the object.

Explain the term fluid.

They lack the ability to offer permanent resistance to deforming particles. They can take form of any solid body it comes into contact with.

What are liquids?

They are almost incompressible and can form free surface.

What are gases?

They are readily compressible and does not form free surface.

What is density of water at 4 degrees celcius?

1000kg/m3 or 1g/cm3

How to conclude if points have the same pressure?

• Same fluid

• Same elevation

• Fluid containing points are connected

What are the SI units?

• meter (m)

• kilogram (kg)

• second (s)

• kelvin (K)

What changes density?

Temperature and pressure.