1. Gravitational Forces What is gravity? Gravity is a force of attraction between objects that have mass. The bigger the mass → the stronger the gravity. The closer the objects → the stronger the gravity. Mass vs Weight Mass Amount of matter in an object Measured in kilograms (kg) Stays the same everywhere Measured with a balance Weight Force of gravity acting on an object Measured in newtons (N) Changes depending on gravity Measured with a spring scale Example Your mass = 50 kg (same on Earth and Moon) Your weight = different (because gravity changes) Formula for Weight F = mg F = weight (N) m = mass (kg) g = gravitational field strength Earth: 9.8 N/kg (≈ 10 N/kg) Example A boy has a mass of 40 kg. What is his weight? F = mg F = 40 × 10 F = 400 N 2. Unit Conversions 1 kg = 1000 g 1 g = 0.001 kg 1 Mg = 1 000 000 g 1 g = 0.000001 Mg Tips kg → g = ×1000 g → kg = ÷1000 g → Mg = ÷1 000 000 Mg → g = ×1 000 000 3. Magnetism Magnetic vs Non-Magnetic Materials Magnetic: iron, steel, nickel, cobalt Non-magnetic: plastic, wood, glass Uses of Magnets Fridges Compasses Electric motors Speakers Magnetic Poles North pole (N) South pole (S) Rule Like poles repel (N–N, S–S) Unlike poles attract (N–S) Magnetic Fields Area around a magnet where force is felt Represented by field lines Field Line Rules Go from North → South Never cross Closer lines = stronger field 4. Electrostatics What is electrostatics? Study of charges at rest Types of Charges Positive (+) Negative (−) Rule Like charges repel Unlike charges attract Charging by Friction When two objects are rubbed together Electrons move from one object to another One becomes negative, the other positive Example Rub a balloon on your hair → it sticks to the wall Interaction of Charges Positive + Positive → repel Negative + Negative → repel Positive + Negative → attract 5. Polarisation (NEW) What is polarisation? Polarisation happens when charges in a neutral object rearrange due to a nearby charged object

What is gravity?

Gravity is a force of attraction between objects that have mass.

What are the factors affecting gravity?

The bigger the mass, the stronger the gravity; the closer the objects, the stronger the gravity.

What is mass?

The amount of matter in an object, measured in kilograms (kg), remains the same everywhere.

What is weight?

The force of gravity acting on an object, measured in newtons (N), and changes depending on gravity.

How is weight calculated?

Weight (F) is calculated using F = mg, where m is mass in kg and g is gravitational field strength.

What is the approximate gravitational field strength on Earth?

Approximately 9.8 N/kg (or about 10 N/kg).

If a boy has a mass of 40 kg, what is his weight?

His weight is 400 N, calculated as F = 40 × 10.

Unit conversion: How many grams are in 1 kilogram?

1 kg = 1000 g.

Unit conversion: How do you convert grams to kilograms?

To convert grams to kilograms, divide by 1000.

What are magnetic materials?

Magnetic materials include iron, steel, nickel, and cobalt.

What are non-magnetic materials?

Non-magnetic materials include plastic, wood, and glass.

Name two uses of magnets.

Magnets are used in fridges, compasses, electric motors, and speakers.

What are the magnetic poles?

The two magnetic poles are the north pole (N) and the south pole (S).

What happens when like magnetic poles come together?

Like poles repel each other (N–N, S–S).

What happens when unlike magnetic poles come together?

Unlike poles attract each other (N–S).

What are magnetic fields?

The area around a magnet where force is felt, represented by field lines.

What direction do magnetic field lines go?

Magnetic field lines go from North to South.

What is electrostatics?

Electrostatics is the study of charges at rest.

What are the types of electric charges?

The two types of electric charges are positive (+) and negative (−).

What happens when like charges come together?

Like charges repel each other.

What happens when unlike charges come together?

Unlike charges attract each other.

What is charging by friction?

Charging by friction occurs when two objects are rubbed together, causing electrons to move from one to the other.

Provide an example of charging by friction.

Rub a balloon on your hair and it will stick to the wall.

How do positive and negative charges interact?

Positive + Positive repel, Negative + Negative repel, Positive + Negative attract.

What is polarisation?

Polarisation occurs when charges in a neutral object rearrange due to a nearby charged object.

What happens to charges in a neutral object during polarisation?

Opposite charges move closer and like charges move further away.

Is a neutral object still neutral after polarisation?

Yes, the object remains neutral overall despite having separated charges.

Provide an example of polarisation.

A charged balloon brought near small paper pieces causes the pieces to move towards it.