SUBJECT: BASIC SCIENCE
TERM: 3RD TERM
TOPIC: MAN IN SPACE
FEELING OF MAN IN SPACE
When a man stands on the floor, his weight acts down on the floor and the floor acts back on the man with a reaction equal in magnitude to his weight. The man feels the reaction from the floor and this makes him aware of how heavy he is. He could actually read his weight by standing on a bathroom-weighing machine. The machine records the value of he reaction on him. If the man carries the machine into a lift and stand on it, the machine gives the same as before for his weight.
The earth is surrounded by a layer of air called atmosphere. This atmosphere is divided into about four regions namely troposphere, stratosphere, ionosphere, and exosphere. The place beyond the atmosphere which is extremely large is called space.
(1) What is the name given to a layer of air that surrounded the earth?
(2) What is the place beyond the atmosphere called?
SUBTOPIC: GRAVITATIONAL FORCE
Gravitational force is a force which attracts bodies towards the earth.
When you throw any object up, it is observed that the object is forced back to the ground. This also accounts for why fruits fall to the ground from the tree, and do not rise upwards again. The earth is behaving like a magnet
Gravity is the force with which the earth attracts objects towards its centre. Gravitation pull comes from this concept of gravity.
SUB-TOPIC: THE GRAVITATIONAL PULL AND WEIGHT
The amount of force with which gravity pulls an object depends on three things namely:
There is difference in weight when an object is weighed on the surface of the earth and when it is weighed high above the earth’s surface. The weight of an object can change as it is moved from one place to another whereas some mass does not change unless some amount of material is taken away from it or added to it.
Weightlessness is a feeling of being weightless. It does not mean having no weight. Weight is the force exerted by the earth on a body. A body is really never weightless of gravitational pull or another.
The scientist are occupied with space travel in order to view the earth and to know how possible is life on the other planets
The force which keeps the body moving round the earth is called centrifugal force. Weightlessness makes object to float freely.
(a) it rotates round the earth
(b) It rotates round the sun
(c) It is close to the earth
(d) It is in the universe
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