高一英语阅读专项：限时阅读--科普说明
An altimeter is an
instrument used in an airplane to tell the pilot how high he is flying.
The altimeter used in most airplanes is a kind of barometer which measures
air pressure. At sea level this pressure is more than 14 pounds on every square
inch of the surface. The higher you go into the air, the lower the air pressure
is. An altimeter measures this air pressure to show how high the airplane is
above the sea level.
But the altimeter does not show how high the plane is above the ground. A
plane might be flying at a height of 15,000 feet, but it would be only a
thousand feet or so above the ground if the land in that area happened to be
14.000 feet above the sea level.
The pilot adjusts(调整)his altimeter to the
actual sea-level pressure before leaving the airport and he corrects it in
flight by new information given to him by radio. He flies high enough to above
any mountain he may pass on his course. The barometer altimeter is correct
within above 300 feet.
Another kind of altimeter, the radio altimeter, makes use of radio
reflection. It calculates the height of the flying plane by sending out
electrical signals to the surface below and measuring the time required for
them to bounce (弹) back. It is correct within 1-5 feet over water, but it
is not reliable over uneven(不平的)land. Big planes
usually have both kinds of altimeters.
1. The following drawing shows a plane flying over a mountain, which of the
heights is given by the barometer altimeter in the plane at the same moment?
2. The barometer altimeter won't work if the plane flies ______ .
A. beyond the atmosphere B. above very high land
C. over very uneven
ground D. with 1,000 feet of
the ground
3. Suppose a plane using a radio altimeter is flying 10,000 meters above a
highland which is 4,000 meters above the sea level. What reading will be given
by the altimeter?
A.10,000 meters. B.4,000 meters.
C.14,000
meters.
D.6,000 meters.
4. Suppose a plane using both kinds of altimeters is flying over a mountainous
area where the land rises and falls very abruptly(陡峭的). The pilot
keeps his plane steady at the same height. Which kind of reading will you get
on each of the altimeters?
A. The readings on both altimeters will remain steady.
B. The readings on both altimeters will rise and fall abruptly.
C. The reading on the barometer altimeter will rise and fall abruptly, while that on the radio altimeter will remain steady.
D. The reading on the
radio altimeter will rise and fall abruptly, while that on the barometer
altimeter will remain steady.
参考答案：C A A D