🌍 Gravitation – Class 9 Physics

Class 9 flashcards for the chapter gravitation use for revision or learning

Gravitation

Force of attraction between two objects in the universe

Universal law of gravitation

F = G × (m₁ × m₂) / r²

F in gravitation

Force of attraction

G in gravitation

Universal gravitational constant

Value of G

6.673 × 10⁻¹¹ N·m²/kg²

m₁ and m₂

Masses of two objects

r

Distance between the centers of the two objects

Gravity

Force with which the Earth attracts objects towards it

Acceleration due to gravity (g)

9.8 m/s² near the Earth's surface

g formula

g = F / m = GM / R²

SI unit of g

Metre per second squared (m/s²)

M in g formula

Mass of Earth (5.972 × 10²⁴ kg)

R in g formula

Radius of Earth (6.4 × 10⁶ m)

Free fall

Motion of an object under only gravitational force

Weight

Force with which Earth attracts a body (W = mg)

Mass

Amount of matter in a body

SI unit of mass

Kilogram (kg)

SI unit of weight

Newton (N)

Weight on Moon

1/6th of weight on Earth

Moon's gravity

1.63 m/s²

Density

Mass per unit volume (ρ = m / V)

Relative density

Density of substance / Density of water

Buoyancy

Upward force exerted by a fluid on a submerged object

Buoyant force

Force acting upward on a body in fluid

Factors on buoyant force

Depends on volume of object and fluid density

Floatation condition

Body floats if its density < fluid's density

Sink condition

Body sinks if its density > fluid's density

Archimedes’ Principle

When a body is immersed in fluid

Applications of Archimedes’ Principle

Ships

Thrust

Force acting perpendicularly on a surface

Pressure

Thrust per unit area (P = Thrust / Area)

SI unit of pressure

Pascal (Pa)

1 Pascal

Pressure of 1 N acting on 1 m²

Pressure in liquids

Increases with depth

Pressure in gases

Exerted equally in all directions

Laws of floatation

A floating body displaces weight of fluid equal to its own weight

Why ice floats

Ice is less dense than water

Why iron sinks

Density of iron > density of water

Fluid

Substance that can flow – includes liquids and gases

Shape of floating object

Affects stability and distribution of buoyant force

Upthrust

Same as buoyant force

U-tube and pressure

More liquid height = more pressure

Submarine working

Changes density by filling tanks with water or air