Text 2 some interesting facts about physics

1. The Air around us is not weightless. In fact, it can be weighed almost as accurately as iron or lead. A column of Air 1 inch square and 600 miles high, for instance, weighs approximately 15 pounds, about twice as much as an average newborn baby. This weight is what creates the phenomenon known as "atmospheric pressure."

2. Sound travels through an object by transferring between molecules. The speed of the sound is dependent on how tight the bonds between the molecules are. The less 'elastic' a material is, the faster the sound moves. For the quoted examples the relevant speeds are: steel, 5100 m/s (meters per second); gold, 3240 m/s; water, 1493 m/s; air, 343 m/s. Diamond allows sound to travel at 12000 m/s which equates to 27000 mph.

3. If you punch a series of holes in a paper cup filled with Water, the Water will squirt out farthest and fastest from the lowest holes. The reason is that Water pressure is greatest at the bottom of the cup. For the same reason, dams are made thicker at the bottom than at the top.

4. The tube used to produce X-rays is called Coolidge tube. It is a device in which high speed electrons, produced from a filament and accelerated by a potential difference, fall on a metal surface(usually a heavy metal)and emit an electron from the L-shell (i.e. the shell with two electrons). This emission of an electon leaves a vacancy or hole in the atom which is filled by an electron moving from a higher energy level which releases energy. This energy is X-ray.

5. A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. A black body in thermal equilibrium (that is, at a constant temperature) emits electromagnetic radiation called black-body radiation. The radiation is emitted according to Planck's law, meaning that it has a spectrum that is determined by the temperature alone, not by the body's shape or composition.

Think about:

• The title of every passage.

• Some other interesting facts about physics.

• The field of physics that is more interesting for you. Why?

• 10 True/False sentences on the text.

• Make up 10 questions on the text and answer your partner’s questions.

Test yourself Test 1

Use Future to complete the sentences

1. Harry / cause / trouble

• Positive:

• Negative:

• Question:

You / copy / the homework

• Positive:

• Negative:

• Question:

The clouds / disappear

• Positive:

• Negative:

• Question:

He / marry / his girlfriend

• Positive:

• Negative:

• Question:

The snowman / melt

• Positive:

• Negative:

• Question:

The people / panic

• Positive:

• Negative:

• Question:

They / react / to my question

• Positive:

• Negative:

• Question: