Ima

Definition:

Earth is the planet we live on. It is our home in space.

Main points :

• Earth is the third planet from the Sun 

• It has air, water, and land, which support life

• Earth has one Moon 

Definition:

Physical quantities are things that can be measured and written using numbers and units.

Examples of Physical Quantities:

• Length – how long something is

• Mass – how heavy something is

• Time – how long an activity takes

What is a Lens?

A lens is a transparent object (made of glass or plastic) that bends light to form images.

1. Convex Lens :

Shape:

• Thick in the middle

• Thin at the edges

  
  

Definition:

A physical quantity is anything that can be measured and has a number and a unit.

Examples :

• Length – how long something is

• Mass – how heavy something is

• Time – how long an activity takes

Definition:

Temperature tells us how hot or cold something is.

Simple explanation:

When something is hot, its tiny particles move fast.

When something is cold, its particles move slowly.

Units of temperature:

A magnet is an object that can attract certain metals like iron, nickel, and cobalt.

It has two ends called poles — a north pole and a south pole.Magnets can pull (attract) or push (repel) other magnets depending on which poles face each other.

Rule:

• Like poles (north–north or south–south) repel each other.

• Unlike poles (north–south) attract each other.

Physical Quantities

• Meaning: Physical quantities are things we can measure in science.

Measurement Techniques

• These are the methods or tools we use to measure physical quantities.For example: Quantities , Instrument Etc

  
  

Electricity is a form of energy that comes from the movement of tiny particles called electrons.

It can make things work, like lights, fans, TVs, and computers, and it flows through wires to reach them.

Acceleration is the rate at speed changes . It tells us how quickly somthing is speeding up or slowing down.

Gravity is a force that pulls objects toward each other.

• On Earth, gravity pulls everything toward the ground — that’s why things fall when you drop them.

• It’s also what keeps us standing on the Earth instead of floating away.

• Gravity is the reason the Moon goes around the Earth and the Earth goes around the Sun.

• The bigger an object is (like Earth or the Sun), the stronger its gravity.

1. Definition:Thermal expansion is the increase in the size (length, area, or volume) of a substance when it is heated. When things get hot, their particles move faster and push each other apart, making the object bigger.

   Examples:

   1. Railway tracks – They have small gaps so that they don’t bend in summer when they expand.

   2. Bridges – They have expansion joints for the same reason.

   3. Thermometer liquid – The mercury or alcohol rises when heated.

   Fun fact:Not everything expands equally. Solids expand less than liquids, and gases expand the most when heated!