40. What is the simplest method of bursting open strong gates?
Suspend a bag of gunpowder containing 50 or 60 lbs., near the middle of the gate, upon a nail or gimlet, having a small piece of port-fire inserted at the bottom, and well secured with twine.
41. What is the length of a pendulum to vibrate seconds, half and quarter seconds respectively?
Seconds, 39.1 inches; half-seconds, 9.8 inches; and quarter-seconds, 2.45 inches.
159]
42. Give a formula for determining the length of the seconds pendulum in any latitude.
| l = | 1 | [32.1803 feet - 0.0821 cos. 2 lat.] |
| 9.8696044 |
43. How are the times of a single oscillation of two pendulums to each other?
As the square roots of their lengths.
44. Repeat the table of measures.