Steel Table

Definition In everyday speech, the word " moment " refers to a short amount of time. In physics and engineering mechanics, moment is the product of a quantity and the distance from that quantity to a given point or axis. For example, in Statics, a force acting on a wrench handle produces a torque, or moment, about the axis of a bolt: M = P ! L. This is the moment of a force. We can also describe moments of areas. Consider a beam with a rectangular cross-section. The horizontal neutral axis of this beam is the x-x axis in the drawing. Take a small area " a " within the cross-section at a distance " y " from the x-x neutral axis of the beam. The first moment of this area is a ! y. The second moment of this area is I x = a ! y () ! y = ay 2. In Strength of Materials, " second moment of area " is usually abbreviated " moment of inertia ". If we divide the total area into many little areas, then the moment of inertia of the entire cross-section is the sum of the moments of inertia of all of the little areas. We can calculate the moment of inertia about the vertical y-y neutral axis: I y = a ! x () ! x = ax 2. The " x " and " y " in I x and I y refer to the neutral axis. This beam has a depth of 16 cm and a width of 5 cm. We can divide the beam into 8 equal segments 2 cm deep, 5 cm wide, so that each segment has an area a = 2 cm ! 5 cm = 10 cm 2. The centroid of segment #1 is 7 cm from the x-x axis y 1 = 7 cm () ; the centroid of segment #2 is 5 cm from the x-x axis y 2 = 5 cm () ; and so on. We can estimate the moment of inertia for the entire area as the sum of the moments of inertia of the segments, written as I x = a i y i 2 1 n ! where n = the total number of segments, and i = the number of each segment (from 1 to n), or:

Tests were carried out to go further into the shape of the bobs (pendulum clock weights). Three different lead weights were tested with different diameter to thickness ratios. The bobs were: 155x2,25 mm, 98x5.1 mm and 58x14.6 mm. All were trimmed to the same weight of 418 grams and balanced around the central mounting hole. A square bob was also made of plexiglas, 155x155x14.7