Gravitation Class 9 Notes Science - Chapter 10

Chapter: 10

https://drive.google.com/file/d/1pByIptFegmQ_eBNKf6mXnPSLhqTKU2FI/view

Force between two objects or bodies which attract each other due to their masses

Effects of Gravity

Free fall

When an object falls down towards the earth under the gravitational force only.
Velocity of free falling body changes and is said to be acceleration due to gravity.
Acceleration due to gravity, ‘g’. Unit is m/s². Value of g = 9.8 m/s².

Equation of Motion	Acceleration due to gravity
v = u + gt	It is the gravitational attraction of earth
h = ut + gt²	g = 9.8 m/s²
v² – u² = 2gh
When a body is dropped freely from a height u = 0, g = 9.8 m/s²

Universal Law of Gravitation

It states that every object in the universe attracts every other object with a force which is proportional to the product of their masses and inversely proportional to the square of the distance only.
F∝(Mm/d²)

F =(GMm/d²) [ ∵ G = Universal gravitational constant]

(where G = gravitational constant, discovered by Cavendish

M = Mass of the earth

R = Radius of the earth)

g =(6.7×10^-11Nm²Kg^–2 ×6 × 10²⁴Kg/(6.4 × 10^–6 m)²)

As the radium of the earth increases from the poles to the equator, the value of g becomes greater at the poles than at the equator.

Mass

Weight

Archimedes’ Principle

When a body is immersed fully or partially in a field, it experiences an upward force that is equal to the weight of the fluid displaced by it.

Applications:

Upthrust	Pressure
When an object is immersed in a fluid, they experience a buoyant force.	Force per unit area
Depends on the density of the fluid.	P =(F/A)
Upward force entered by liquid on a body.	Pressure =(Thrust/Area)
Density of object < density of liquid ⇒ object floats.
Density of object > density of liquid ⇒ object sinks.