Passage 37

There are many reasons for the tidal action which is a very complicated phenomenon involving many factors all of which must be considered to predict tide in any one place and at any one time. The alternate rise and fall of the surface of the seas and the ocean is mainly caused by the attractive force of the moon alone. When the attraction is great, the tide is high; and conversely when the attraction is minimal, the tide is low. Between the high tide and the low tide is a period of a little over six hours, being called during its rise a flood tide, and during its fall an ebb tide.

The sun also exerts its effect on the tide, being a little less than half as much as the moon, although its mass is so much greater. When the moon and the sun are horizontal, the highest high tide occurs and when they are vertical the lowest low tide takes place.

The wind also plays an important part in the modification of the normal rise and fall of the tide. Thus these factors affect each other, either distracting or adding to the attractive forces to add of subtract from the height of the tide. But the tides still move inexorably on, rising twice a day, getting a little late each day and posing a problem of correctly predicting their heightsand lows.

  1. Which of the following factors will affect the action of the tide?

    1. The sun.

    2. The moon.

    3. The wind.

    4. All of the above mentioned factors.

  2. The principal idea of the article is .

    1. the attraction of the sun and the moon

    2. the changing tide

    3. the sun, the moon and the wind

    4. the factors affecting the tide

  3. Which of the following factors is not mentioned as affecting the

    tide?

    1. The sun.

    2. The moon.

    3. The winds.

    4. The depth of the ocean.

  4. It can be concluded from this article that the attraction of the

sun is .

  1. less than half that of the moon

  2. more than half that of the moon

  3. more than that of the moon

  4. less than twice that of the moon

  1. According to the article, it is clear that the force of the moon

.

  1. is not as important as that of the wind

  2. is less than half as much as the sun

  3. causes the alternate rise and fall of the surface of the seas

  4. does not influence the rise and fall of the surface of the seas