gravity

• Gravitation is the motion of objects under the influence of gravitational force on the earth.
• The weight of a body varies from place to place.
• Conditions for objects to float in liquids can be discussed.
• Gravitation is responsible for the motion of planets, the moon, and all other objects in the universe.
• The universal law of gravitation 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 between them.
• The force is along the line joining the centres of two objects.
• A stone when thrown upwards, reaches a certain height and then falls downwards.
• Isaac Newton could grasp that the same force is responsible for the motion of planets, the moon, and all other objects in the universe.
• The force responsible for the motion of planets, the moon, and all other objects in the universe is called the gravitational force.
• Gravitation is responsible for the motion of objects under the influence of gravitational force on the earth.
• The weight of a body varies from place to place.
• Conditions for objects to float in liquids can be discussed.
• Gravitation is responsible for the motion of planets, the moon, and all other objects in the universe.
• The weight of an object on the moon is 1/6 its weight on the earth due to the lower gravity on the moon.
• Thrust and pressure are important concepts in understanding the phenomena of camels running in deserts, army tanks resting on continuous chains, trucks and motorbuses having wider tyres, and cutting tools having sharp edges.
• Thrust is the force acting perpendicular to the surface of an object.
• Pressure is the thrust acting on a unit area.
• The SI unit of thrust is N/m 2 or N m –2.
• The SI unit of pressure is N/m 2 or N m –2.
• The SI unit of pressure is named after scientist Blaise Pascal and is denoted as Pa.
• A block of wood kept on a tabletop exerts a pressure of 2450 N m -2 when it is made to lie on the tabletop with its sides of dimensions 20 cm × 10 cm.
• When the block lies on its side of dimensions 40 cm × 20 cm, it exerts the same thrust.
• The universal law of gravitation 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 between them.
• The force is along the line joining the centres of two objects.
• Gravitational force is the force of attraction between two bodies due to the presence of mass.
• Gravitational force is denoted by 'F'.
• The unit of 'F' is the same as that of acceleration, that is, 'm s^-2'.
• According to the second law of motion, force is the product of mass and acceleration.
• The magnitude of the gravitational force 'F' will be equal to the product of mass and acceleration due to the gravitational force, that is, 'F = m g'.
• Water exerts a force on the bottle in the upward direction.
• From equations '(10.4) and (10.6)', '2 = G M m m g d' or 'G^2 M g = d'.
• The upward force exerted by the water increases as the bottle is pushed deeper until it is completely immersed.
• For objects on or near the surface of the earth, 'G^2 M g = R'.
• When the bottle is released, it bounces back to the surface.
• As the radius of the earth increases from the poles to the equator, the value of 'g' becomes greater at the poles than at the equator.
• The force due to the gravitational attraction of the earth acts on the bottle in the downward direction.
• All objects, regardless of their hollowness, size, or mass, should fall at the same rate due to gravity.
• The bottle is pulled downwards by the force due to the gravitational attraction of the earth.
• Gravitational force is independent of the mass of the object.
• The water exerts an upward force on the bottle, thus, the bottle is pushed upwards.