Gravitation Class 9 Notes Science - Chapter 10
What Are Gravitation ?
Force between two objects or bodies which attract each other due to their masses
Effects of Gravity
• 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.
Equation of Motion
• v = u + gt
- When a body is projected vertically upward with an initial velocity, u, than g = –9.8 m/s2
Acceleration due to gravity
• It is the gravitational attraction of earth
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.
Relation Between g And G
M = Mass of the earth
R = Radius of the earth)
• 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 And Weight
• Mass of an object is the measure of its inertia. (Scaler quantity)
• It remains the same everywhere in the Universe.
• SI Unit : Kg
• Weight is the force of attraction of the earth on the object (vector quantity)
• Weight of the body changes form place to place
• W = mg
• SI Unit: Newton (N)
• Net force applied in a particular direction.
• Depends on the area on which it acts.
• SI Unit: Newton
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.
• Used in designing ships and submarines
• Used in lactomoters to find purity of milk.
• Used in hydrometer to determine density of liquid.
• When an object is immersed in a fluid, they experience a buoyant force.
• Depends on the density of the fluid.
• Upward force entered by liquid on a body.
• Density of object < density of liquid ⇒ object floats.
• Density of object > density of liquid ⇒ object sinks.
• Force per unit area
• P =(F/A)
• Pressure =(Thrust/Area)