Title : Law of Moment
Aim: The verification of principle of moments.
Apparatus: Drawing sheet, pins, mirrors, weight pan, weights and pulleys.
Theory: The moment of a force at a point is equal to the product of force and the perpendicular distance of the point from the line of action of the force. Principle of moment states that the moment of the force about a point is equal to sum of the moments of its components about the same point. Geometrically the moment of the force is equal to twice the area of the triangle whose base is the line representing the force.
Procedure:
- Two pulleys are mounted on a board, which is fixed on a wall. A string is passed through both the pulleys. Another string is tied to this string at the center of the pulleys. Weight pans are attached to the two ends of the string.
- Fix a drawing sheet on the board. Add weights in any two pans in such a way that the sum of the weights in any two pans is greater than the third. The system of forces will come to equilibrium on some part of the drawing sheet.
- Take a mirror and place it behind the strings. Mark the images of the strings on the drawing sheet
- Remove the drawing sheet and find the resultant of the two forces graphically. Change the weights and repeat the procedure for a different set of weights
- After completing the parallelogram, consider any point O which is the moment centre. Join all the corners of the parallelogram to this point O, to form triangles
- Find the areas of the triangles so as to verify the principle of moments.
Observation Table :
| Sr. No. | P1 | d1 | P2 | d2 | M1=P1d1 | M2=P2d2 | ∑M |
|---|---|---|---|---|---|---|---|
| 1 | 200 | -10 | 100 | 20 | -2000 | 2000 | 0 |
| 2 | 200 | -15 | 100 | 30 | -3000 | 3000 | 0 |
| 3 | 50 | -20 | 100 | 20 | -1000 | 1000 | 0 |
| 4 | 200 | -40 | 200 | 40 | -8000 | 8000 | 0 |
Result: Law of moment is verified.
Calculator
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