Q1: What is the centre of gravity apparatus used for?
The FX-504 centre of gravity apparatus is used to experimentally locate the centre of gravity of flat laminas of various shapes. Students suspend each lamina from a pin, use a plumb bob to mark the vertical line of action of the object’s weight, repeat the process from a second hole, and identify the CG as the intersection of the two lines. Results are then compared with values from standard formulas or reference tables to validate the experimental method.
Q2: What shapes are included with the FX-504?
The FX-504 is supplied with six lamina shapes: a circle, an isosceles triangle, a trapezium, an L-shape, a T-shape, and a semi-circle. The set includes both regular shapes — whose CG positions can be calculated using standard geometric formulas — and compound shapes, where the CG location is less obvious and the experimental method is particularly informative.
Q3: What is the plumb bob method for finding centre of gravity?
The plumb bob method involves suspending a flat object freely from a pin and allowing it to come to rest. A plumb bob hung from the same pin defines the vertical line passing through the centre of gravity of the object. This line is marked on the object’s surface. The object is then rehung from a different point, generating a second line. The centre of gravity lies at the intersection of these lines. The method is reliable for objects of uniform thickness and uniform density.
Q4: Can the centre of gravity lie outside the physical boundary of a shape?
Yes. For compound shapes such as L-sections and T-sections, the calculated and experimentally determined centre of gravity often lies in the void area between the limbs of the shape — outside the actual material boundary. The FX-504 demonstrates this directly, as the intersection of the plumb lines falls in an empty region of the lamina. This is an important concept in structural section design and reinforces why the experimental method is a valuable complement to analytical calculation.
Q5: What is included in the scope of delivery for the FX-504?
The FX-504 is supplied as a complete experimental kit including: one experimental unit (free-standing backboard with suspension pin), six lamina samples (circle, isosceles triangle, trapezium, L-shape, T-shape, semi-circle), one plumb bob, one thread, and one instructional manual containing assembly details, experimental procedure, application notes, and example test results.