Introduction to physics for students

Understanding Physics

Understanding Physics

1. Like all sciences, physics is based on experimental observations and quantitative measurements.

Understanding Physics

2. Historically, until nineteenth century, physics was called natural philosophy.

Understanding Physics

3. Physics is a branch of science concerning study of natural phenomena, that is, properties of matter and energy.

Understanding Physics

• 4. Some examples of natural phenomena are

(a) sunrise and sunset, (b) lightning and thunder, (c) rainbow and blue sky, (d) earthquake and tsunami.

Field of study in Physics

In general, physics is concerned with the study of energy and the properties and structure of matter.

Field of study in Physics

Physics

Classical Modern

Field of study in Physics

• deals with questions regarding motion and energyMechanics (forces and motion)HeatSoundEelectricity and magnetism Light

Physics

Classical Modern

Field of study in Physics

• concentrates on scientific beliefs about the basic structure of the material world

Physics

Classical Modern

Understanding Base Quantities and Derived Quantities

Base Quantities

• 1. Physical quantities are quantities that can be measured.

Base Quantities

2. A physical quantity can be represented by a symbol of the quantity, a numerical value for the magnitude of the quantity and the unit of measurement of the quantity.

Length, l = 1.67 ml - symbol 1.67is the value m - unit

Base Quantities

• 3. Base quantities are physical quantities that cannot be defined in terms of other quantities.

Base quantity :Length

Derived quantity :Area = length x length

Base Quantities

Base quantities SI base units

Name Symbol Name Symbol

Length l Metre m

Mass m Kilogram Kg

Time t Second s

Electric current

I Ampere A

Temperature T Kelvin K

Derived Quantities

1 Derived quantities are physical quantities derived from base quantities by multiplication or division or both. The unit for a derived quantity is known as a derived unit.

Derived Quantities

takenTime

ntDisplaceme

takenTime

velocityinChanges

ms -1

volume

Mass kg

m3

Derived quantities Derived units

Area = Length x breadth [Area] = m x m = m2

Velocity = [Velocity] = = ms–1

Acceleration=

Density = [Density] = = kgm–3

m

s

[Acceleration] = = ms–2

Vectors and Scalars

ScalarA SCALAR is ANY quantity in

physics that has MAGNITUDE, but NOT a direction associated with it.

Magnitude – A numerical value with units.

Scalar Example

Magnitude

Speed 20 m/s

Distance 10 m

Age 15 years

Heat 1000 calories

Temperature 37OCMass 100kg

Volume 5m3

VectorA VECTOR is ANY quantity in

physics that has BOTH MAGNITUDE and DIRECTION.

Vector Magnitude & Direction

Velocity 20 m/s, NAcceleration 10 m/s/s, EWeight 100N

(toward center of the earth)

Force 5 N, West

Fav,,

Vectors are typically illustrated by drawing an ARROW above the symbol. The arrow is used to convey direction and magnitude.