College Laboratory Manual of Physics

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: PENDULUMS Value Of g By Simple Pendulum The simple pendulum as here used is a sphere of lead, about 1 cm. in diameter, suspended by a fine silk thread from the beveled edge of a wooden shelf, S, Fig. 6. The length, I, of the pendulum may, with sufficient f accuracy for our present purpose, be measured from the lower edge of the shelf to the centre of the ball. It is well to have I as great as 100 cm. The width of the swing should be small, perhaps 5 cm. each way from the middle. Take the time required for 100 single swings, and so find t, the time of one swing. Then from the formula the value of g is readily found. Properties Of Reversible Pendulum. 1. In Fig 7 and Fig. 8 R is a meter-rod having a short cylindrical cross-bar, 6, fixed permanently near one end, and a similar cross-bar, 62, adjustable at any position along a slot of considerable length in the lower half of the rod.Near the lower end of the rod there may be a metal bob, B. If the slot in R is properly placed, it is possible to fix 62 in such a position that R will vibrate in precisely the same time when suspended, inverted, from 62, as when suspended in the position shown by Fig. 7. Accordingly R, with its attachments, is called a reversible pendulum. To show this reversibility, place 62 at the middle of the slot and hang alongside, as in Fig. 7, a simple pendulum, having the centre of the ball just on a level with the upper side of 62. The length of the simple pendulum, as previously defined, is now equal to the distance between the under side of 6, and the upper side of 62. Set the two pendulums vibrating together. If the simple pendulum is the slower, shorten it, and move 62 up accordingly; and vice versa. Continue the trials until the time of vibration of the two pendulums is the same. It...