16 ANSWERS TO PRACTICAL QUESTIONS 



ity in the former need not be raised much to bring the line of 

 direction without the base, while in the latter it must be. 



1 0. Why is a pyramid the stablest of structures ? 



Because the base is so broad and the center of gravity so 

 low. The center of gravity must therefore be lifted very high 

 before the line of direction will fall without the base. 



11. When a hammer is thrown, on which end does it 

 most often strike ? 



The heavier end. 



12. Why does a rope-ivalker carry a heavy balancing- 

 pole? 



Because in this way he can easily shift his center of 

 gravity. 



13. Wliat would become of a ball if dropped into a hole 

 bored through the center of the earth ? 



If we assume the earth to be at rest, the ball will move 

 with diminishing acceleration, but increasing speed, to the cen- 

 ter. The momentum thus acquired would carry it an equal 

 distance beyond, if there be no resistances, and the acceleration 

 being now negative, the ball will be brought momentarily to 

 rest at the surface on the opposite side. It will then fall back 

 past the center, and continue thus oscillating forever. If we 

 assume the earth to be rotating, the ball will sink from fast- 

 moving toward slow-moving parts, and strike against the side 

 of the hole. Friction will soon bring it to rest at the earth's 

 center. 



1. Would a clock lose or gain time if carried to the top 

 of a mountain ? 



i It would lose time, because the force of gravity would be 

 lessened. At the North Pole it would gain time, because there 

 the force of gravity would be increased. 



15. In the winter, would you raise or lower the pendu- 

 lum-bob of your clock? 



