# Man's physical universe

100 THE UNIVERSE A VAST SYSTEM OF PARTS

Similar equipment is used in sugar refineries and many other industries

to remove crystals from the liquids in which they are formed.

The Babcock milk-tester and cream-separator separates the cream

from the denser portions of the milk because the denser portions, with

greater inertia, have a greater centrifugal tendency and resistance to

centripetal acceleration. This tendency is also applied in centrifugal

water pumps, the governors of engines, and the cowboy's lariat.

And finally, it is this same centrifugal resistance to centripetal

acceleration that causes the earth to bulge at the equator.

STUDY QUESTIONS

1. State Newton's laws of motion and illustrate each by a concrete example not

given in the text.

2. Upon what two things does the measure of attraction between two bodies

depend?

3. State Newton's law of universal gravitation.

4. Give evidence that Newton's laws of motion are inv'ariable.

5. Differentiate between mass and weight.

6. Why does the earth not travel in a straight line through space relative to the

position of the sun?

7. Give an illustration of an application of centrifugal force in the home.

8. Give five illustrations of the application of centrifugal force.

9. \\ hat is centrifugal force?

10. What keeps the earth in its orbit?

11. Would a planet of large mass have to move more or less rapidly than a planet

of smaller mass to enable its centrifugal force to balance the force of attraction

of the sun?

12. Pluto is a small planet like the earth, but it is much farther from the sun than

the earth. Does it move more or less rapidly than the earth?

13. W'hy is it advisable to slow down on turns?

14. Why is it thought that the companion of Sirius is composed of very dense

matter?

15. State and illustrate Newton's first law of motion, i.e., the law of inertia.

16. State and illustrate Newton's second law of motion, i.e., the law of force.

17. State and illustrate Newton's third law of motion, i.e., the law of action and

reaction.

18. What is weight, and how is it measured?

19. W'hat is mass, and how is it measured?

20. What is force, and how is it measured?

21. Use the terms force, velocity, and acceleration in describing the motion of

an automobile.

22. Explain the tides.

23. Explain the precession of the earth.

24. Describe an exp)eriment which seems to confirm Einstein's suggestion that

space is curved.

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