NEWTON EXPLAINS MOTION

Date: 2015-10-07; view: 443.

Ex.14. Read and translate the following text.

Ex.13. Make a short report on the basis of the text “Some Notions about Motion” paying special attention to the contributions of Aristotle, Galileo and I. Newton mentioned.

Ex.12. Put special and alternative questions to the text “Some Notions about Motion” and ask your group-mates to answer them.

TEXT

Although many scientists studied motion, it was a great British physicist Sir Isaac Newton who formulated the theories of motion, verified them and before that he extended the earlier works by a great Italian scientist Galileo Galilei and a great Polish scientist Nicholas Copernicus.

First Newton studied the quality of inertia, or the tendency of a body to resist change in its state of motion or direction. A tennis ball, for example, has a little inertia. It's very easy to get to move, stop, or change its direction. A truck, on the other hand, has a great deal of inertia. Newton concluded that a body at rest will remain at rest and that a body in motion will remain in motion unless some outside force acts on it. This principle is called the Law of Inertia, or Newton's first law of motion.

But Newton didn't satisfy his great curiosity. He asked a number of questions and he wanted to answer them.

First, why does a body at rest begin to move or in motion change its direction?

Newton tried to determine that if a body is at rest, then no force is acting on it. But when a force acts on a body, the body changes its direction or it slows down or speeds up.

Newton also discovered that there is a certain relationship between force and acceleration. If you push a swing gently, it will move slowly. But if you push it harder, it will go faster. Newton also noted that if you discount the friction involved, then the amount of force is in certain relation to the amount of acceleration.

The acceleration is also related to the mass of an object. Mass which is the quantity of mater in a body, also determines the amount of inertia the object has. A truck has a great deal of mass and a bicycle has much less.

The larger is the mass, the less is the acceleration of an object. In fact, the acceleration of a body is inversely proportional to its mass. Newton's second law of motion states that the acceleration of a body is in direct relation to the force acting on it and inversely proportional to its mass. The direction of acceleration is in the direction of the applied force.

Finally, Isaac Newton explored the question of the source of force. He observed that the force which acts on a body comes from another body. But this idea by itself was not consistent with his view of a balanced and symmetrical universe. He therefore concluded that whenever there is a force which pushes a body in one direction, there is another force which pushes the body in the opposite direction. This concept may be difficult to imagine but try pulling on a rubber band and you will feel it pulling back on you. Also try to notice what happens to your finger when you press it against a table. Objects can exert a force because all materials are elastic to some extent, although the elasticity of walls and tables may be very slight. When you push off the wall of a swimming-pool, you start to move away from the wall. The wall is exerting the force on you that causes you to move in the opposite direction. Thus Sir I. Newton stated his third law: whenever an object exerts a force on the second object, the second object exerts an equal and opposite force on the first object.

The movement of a rocket is also based on this law. The rocket expels gases, which then exert an equal and opposite force, propelling the rocket forward. In space a vehicle can alter its speed or direction by expelling rockets in the opposite direction.

Ex.15. Translate the following words and word combinations into Russian:

to formulate the theories of motion; to verify theories; to resist change; a great deal of inertia; outside force; to satisfy one's great curiosity; to determine; to slow down; to speed up; a certain relationship between; to push a swing gently; to push smth. harder; to be in direct relation to the amount of acceleration; to be inversely proportional to; to explore the question of; to be consistent with one's view; a balanced and symmetrical universe; to push a body; in the opposite direction; to pull back; to exert a force; to expel gases; to propel the rocket forward; to alter speed or direction of a body.

Ex.16. Answer the following questions:

a) Who formulated the theories of motion?

b) Whose earlier works did I. Newton extend while formulating these theories?

c) First Newton studied the quality of inertia, or the tendency of a body to resist change in its state of motion or direction, didn't he?

d) What is another name for Newton's first law of motion?

e) Did I. Newton also discover that there is a certain relationship between force and acceleration or between force and mass?

f) What happens if you push a swing gently?

g) The acceleration is also related to the mass of an object, isn't it?

h) Is the acceleration of a body inversely or directly proportional to its mass?

i) Who explored the question of the source of force?

j) What happens when you try pulling on a rubber band?

l) Why can objects exert a force?

m) Is the elasticity of walls and tables very great or very slight?

n) What must happen when you push off the wall of a swimming-pool?

Ex.17. Agree or disagree with the following statements:

a) It was a great British physicist Sir Isaac Newton who formulated the theories of motion.

b) Inertia means the tendency of a body to resist change in its state of motion.

c) A tennis ball has a very large inertia.

d) A very big object such as a truck doesn't have any inertia at all.

e) It was N. Copernicus who discovered that there is a certain relationship between force and acceleration.

f) Newton's first law of motion is also known as the Law of Inertia.

g) If a body is at rest, then very many forces are acting on it.

h) If you push a swing gently, it will move slowly and if you push it harder, it will go faster.

i) Mass which is the quantity of matter in a body, doesn't determine the amount of inertia the object has.

j) The larger is the mass, the less is the acceleration of an object.

k) The acceleration of a body is inversely proportional to its mass.

l) Newton's second law of motion states that the acceleration of a body is in direct relation to the force acting on it and is inversely proportional to its mass.

m) Isaac Newton never explored the question of the source of force. It was G. Galilei who did it.

n) When you push off the wall of a swimming-pool, you start to move away from the wall.

o) Newton's third law of motion states that whenever an object exerts a force on the second object, the second object exerts an equal and opposite force on the first object.