# Science & Technology

Here is the first set of study material for physical science:

1. Physical quantities are measured in unit. Units are of two types. They are: i) Fundamental units, ii) Derived units.Fundamental units can be expressed without the help of other units. Ex: Length,Mass,Time.Derived units are expressed with the help of other units. Ex. Velocity,Speed,Work,Volume.There are four standards of measurement units. They are, CGS, FPS, MKS, SI.

In SI units, there are seven fundamental units. They are:

 Sl No. Physical quantity SI Unit Symbol 1 Length metre m 2 Mass kilogram kg 3 Time second s 4 Electric Current ampere A 5 Temperature kelvin K 6 Luminous Intensity candela Cd 7 Amount of substance mole mol

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There are two supplementary units barring this list. They are the unit of plane angle; Radian(Rad) and the unit of solid angle; Steradian(sr).

Large units of length are: Light Year, AU (astronomical Unit) and Persec.

Small units of lengths are: Angstrom, Fermi, micro metre(mt.),nano mt.,pico mt.,femto mt. etc.

Large mass units are: Mt. Ton, Chandrasekhar limit and small mass units is: Atomic mass unit or Dalton.

Unit of time: Solar day, lunar month.

Physical quantities can also be divided into two types. They are: Scalar quantities and Vector Quantities.

Scalar quantities have only magnitude and no direction. Ex. Mass, Speed, Work, Time, etc.

Electric current though has direction, it’s a scalar quantity as it does not obey the triangle law.

Vector quantities have both, magnitude and direction and obey the triangle law. Ex. Displacement, Velocity, Acceleration, Force, Momentum, Torque.

Scar and vector are both tensor quantities. Scalar=tensor of rank 0, Vector= tensor of rank 1.

Displacement: Shortest distance covered by a moving body in a definite direction. Unit: m, cm

Distance: Length of actual path covered by a moving object in a given interval. Unit: m, cm.

Displacement can be 0, positive and negative but distance cannot be 0 of a moving object.

Speed: Distance travelled by a moving object in unit time interval. Speed=distance/ time. Unit: m/s, cm/s.

Velocity: displacement of a moving object in unit time interval. velocity= displacement/time. m/s, cm/s.

Acceleration: Rate of change of velocity of a moving object. Unit: m/s² , cm/s².

Acceleration=change in velocity/time. If velocity decreases with time, it is called retardation.

Read Newton’s Laws of Motion. They were published in the book named Philosophiæ Naturalis Principia Mathematica.

Force: It is the cause which changes or tries to change the state of a body. Unit: Dyne (CGS) and Newton (SI).  1 N= 10^5 Dyne. P(force)= mass of a body(m) X acceleration of the body(f) [p=mf]

The property of a body which resist the applied force on it is called Inertia. The inertia of a body in rest is called Inertia of rest and the inertia of a body in motion is called the Inertia of motion. Because of inertia the passengers of a moving car tends to go down when the car stops suddenly (inertia of motion).

Impulse: A force of high magnitude when work on a body for a very small span of time, it is called Impulse or impulsive force.

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You can give your feedback below. Subscribe for update of new study materials and other information in www.icsgwbcs.com. Copyright © ICSG-2017 All rights reserved. Work: If a body gets displaced when a force acts on it, work is said to be done.

Work= Force(f) X Displacement(S). Unit: Joule (SI) Erg (CGS). [W=FS]. Work is a scalar quantity which is a product of two vector quantities namely force and displacement.

When the displacement of a body occurs at the right angle with the direction of the applied force, then work done =0 even if energy is required to carry out the task.

Energy: Capacity of doing work of a body is called energy. Energy is a scalar quantity and its units are Joule(SI) and Erg(CGS).

Mechanical energy: Energy developed in a body due to work done on it is called mechanical energy. It is of two types, they are: i) Potential energy ii) Kinetic energy.

Potential energy: The capacity of work developed in a body due to its position or configuration. Ex. Energy of compressed spring or stretched spring.

Energy of a body kept at a height above the earth surface. It is measured by: P.E= mgh. m= mass of body, g=acceleration due to gravity and h=height of the body from the earth surface.

Kinetic energy: The energy possessed by a body due to its motion. Ex. Energy of a moving car.

K.E is measure by: K.E=½ mv². M=mass of the moving body, v= velocity of the body

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