HBSE 9th Class Science Notes Chapter 10 Gravitation

Haryana State Board HBSE 9th Class Science Notes Chapter 10 Gravitation Notes.

Haryana Board 9th Class Science Notes Chapter 10 Gravitation

→ The fall of an apple from a tree and motion of moon is due to gravitational force.

→ Sir Isaac Newton discovered the law to define gravitational force.

→ Sir Isaac Newton was bom in 1642.

→ A body moving with velocity v in a circular track of radius r is directed towards the centre of earth with an acceleration of \(\frac{v^2}{r}\)

→ The force of gravity decreases with altitude. It also varies on the surface of the earth, decreasing from poles to the equator.

→ The value of universal gravitational constant G is 6.673 × 10-11 Nm2/kg2.

HBSE 9th Class Science Notes Chapter 10 Gravitation

→ According to Newton, the motion of planets is due to that gravitational force which sun imposes on them.

→ The centre of gravity of objects having regular shape and same density lies on their geometrical centre.

→ The force of attraction of earth on an object is directed towards its (earth) centre.

→ The weight of an object is equal to the product of mass and acceleration due to gravity.

→ The weight of an object can be different at different places, but mass remains constant.

→ All objects experience a force of buoyancy when they are immersed in a fluid.

→ Objects having density less than that of the liquid in which they are immersed, float on the surface of the liquid. If the density of the object is more than the density of the liquid in which it is immersed, then it sinks in the liquid.

→ The value of acceleration due to gravity of earth is 9.8 ms-2.

→ The maximum horizontal distance covered by a projectile is called range.

→ Weight of an object always acts in vertical direction.

→ The weight of an object on moon is \(\frac{1}{6}\) th times in comparison to that of earth.

→ SI unit of thrust is newton (N).

→ SI unit of pressure is newton per metre square (Nm-2). In honour of scientist Blaise Pascal, the SI unit of pressure is called pascal, denoted as Pa.

→ The relative density of an object is the ratio of its density and density of water.

→ All objects experience a bouyant force when immersed in fluid (liquid or gas).

→ SI unit of density is kilogram per metre cube (kgm-3).

→ The density of the sample of a substance helps in the measurement of its purity.

→ The relative density of gold is 19.3.

→ Relative density has no unit because it is a ratio.

→ Gravitational Force: Any two particles of the universe attract each other with a force which is called gravitational force.

HBSE 9th Class Science Notes Chapter 10 Gravitation

→ Force of Gravity: The gravitational force applied by earth is called force of gravity.

→ Centripetal Force: The acceleration which maintains the circular motion is always directed towards the centre of circle, which is called centripetal force.

→ According to Law of Gravitation: 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 between them. This law is applicable to all objects anywhere in universe. Such type of law is called universal law.

→ Centre of Gravity: The force of gravity on a body can be considered to active on a point in body. This point is called the centre of gravity of the body.

→ Weight: The weight of the body is that force by which the earth attracts that body.

→ Projectile: A particle thrown at any angle from vertical is called projectile. Its path is curved which is called parabolic path or parabola.

→ Mass: The mass of a body is the measure of its inertia.

→ Thrust: The force acting perpendicular to the surface of the body is called thrust.

→ Pressure: The trust exerted per unit area is called pressure. That is, pressure = \(\frac{\text { thrust }}{\text { area }}\)

→ According to the Principle of Archimedes’: When a body is immersed fully or partially in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by it.

HBSE 9th Class Science Notes Chapter 10 Gravitation

→ Buoyant Force: When a body is immersed in a fluid, a force is exerted by the fluid on body in upward direction which is called buoyant force.

→ Density: The mass per unit volume is called density.

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