Units and Measurement

Measurements, Dimensions, Errors

What are physical quantities?

All the quantities that can be measured.

What is measurement?

It is the comparison of a quantity with a standard of the same physical quantity.

What are scalars?

Physical quantities that only have magnitude and no direction.

What are vectors?

Physical quantities that have both magnitude and direction, and also obey laws of vector algebra.

What are fundamental or base quantities?

A set of physical quanitites that are completely independent of each other and all other physical quantities can be expressed in terms of these physical quantities.

What are derived quantities?

Physical quantities that can be expressed in terms of the fundamental quantities.

What sort of quantity is mass?

Fundamental and Scalar.

What sort of quantity is time?

Fundamental and Scalar.

What sort of quantity is displacement?

Fundamental and Vector.

What sort of quantity is speed?

Derived and Scalar.

What sort of quantity is pressure

Derived and Scalar.

What sort of quantity is work?

Derived and Scalar.

What sort of quantity is force?

Derived and Vector.

What sort of quantity is velocity?

Derived and Vector.

What sort of quantity is acceleration?

Derived and Vector.

What are the four basic properties of units?

1. They must be well-defined

2. They should be easily available and reproducible

3. They should be invariable

4. They should be accepted to all

FPS or British Engineering System

foot pound second

CGS or Gaussian System

centimeter gram second

MKS System

metre kilogram second

State the SI units of the following quantities:

1. Length

2. Mass

3. Time

4. Temperature

5. Electric Current

6. Luminous Intensity

7. Amount of Substance

1. metre (m)

2. kilogram (kg)

3. second (s)

4. Kelvin (K)

5. ampere (A)

6. candela (cd)

7. mole (mol)

Plane Angle Formula

l = rθ

Solid Angle Formula

A = r²θ

What are significant figures?

The reliable digit plus the first uncertain digit in a reported measurement.

do you know all these rules determining the number of significant figures?

Yes.

What is the purpose of scientific notation?

To remove ambiguities in determining the number of significant figures.

How does multiplication and division affect the number of significant figures?

Answer has the same number of significant figures as there are in the original number with the least significant figures.

How does addition and subtraction affect the number of significant figures?

Answer should retain as many decimal places as are there in the number with the least decimal places.