Activity 1
A
If the mass of the earth is M, R its radius and m is the
mass of an object placed on the surface of the earth.
The force of attraction between them is
с C
R?
Points A and C represents different positions on the
surface of the earth. Point B represents the centre of the earth.
a)
At which point on the surface of earth does a body experience maximum weight?
b) At which point does the body experince zero weight?
c) Does the weight of an object increase or decrease as it moves from A to C?
d) What is the reason why the weight of objects vary in different places on the surface of the
earth why?
Answers
Answer:
What do aching feet, a falling apple, and the orbit of the Moon have in common? Each is caused by the gravitational force. Our feet are strained by supporting our weight—the force of Earth’s gravity on us. An apple falls from a tree because of the same force acting a few meters above Earth’s surface. And the Moon orbits Earth because gravity is able to supply the necessary centripetal force at a distance of hundreds of millions of meters. In fact, the same force causes planets to orbit the Sun, stars to orbit the center of the galaxy, and galaxies to cluster together. Gravity is another example of underlying simplicity in nature. It is the weakest of the four basic forces found in nature, and in some ways the least understood. It is a force that acts at a distance, without physical contact, and is expressed by a formula that is valid everywhere in the universe, for masses and distances that vary from the tiny to the immense.
The figure shows a graphic image of a person sitting under a tree carefully looking toward an apple falling from the tree above him. There is a view of a river behind him and an image of the Sun in the sky.
Figure 1. According to early accounts, Newton was inspired to make the connection between falling bodies and astronomical motions when he saw an apple fall from a tree and realized that if the gravitational force could extend above the ground to a tree, it might also reach the Sun. The inspiration of Newton’s apple is a part of worldwide folklore and may even be based in fact. Great importance is attached to it because Newton’s universal law of gravitation and his laws of motion answered very old questions about nature and gave tremendous support to the notion of underlying simplicity and unity in nature. Scientists still expect underlying simplicity to emerge from their ongoing inquiries into nature.
Sir Isaac Newton