To verify the law of Lami's theorem and Triangle of forces.

Aim

To verify the law of Lami's theorem and Triangle of forces.

Theory:

Law of Triangle of forces states that “If three coplanar, concurrent forces are in equilibrium, the forces can be represented in magnitude and direction by the sides of triangle drawn in such a way that the sides of triangle are parallel to the forces taken in order”.

If two coplanar ,concurrent forces acting on a particle is represented in magnitude and direction by the two sides of a triangle, taken in order, their resultant can be represented in magnitude and direction by the third side of the triangle but in opposite order.

Lami's theorem states that “If three coplanar concurrent forces acting on a body are in equilibrium, then each force is directly proportional to the sine of angle between the other two forces”.

Apparatus Used:

1. Board with pulleys
2. Stepped weights hanger
3. Strings,
4. Weights
5. Drawing Sheets

Procedure:

1. Take two wire apparatus and fix drawing sheet on the board.,
2. Connect the hanger at the end of each string and hang the given weight on the pivot provided.
3. Note down the reading of the two spring balances and weight F2 so that equilibrium condition is achieved.
4. Mark the position of strings on the drawing sheet using mirror after equilibrium condition is reached.
5. Note down magnitudes of weight F1, F2 and F3 in the table.
6. Repeat the above procedure for various sets of readings.
7. Measure magnitude of resultant6 force R graphically for verification of triangle law.
8. Measure the angle α, β, and γ for verification of Lamis theorm,

Observations And Calculations : Law of Triangle of Forces

Observations And Calculations : Lami`s Theorem

Result:

1. Lami's Theorem of forces- ________________(Verified /Not verified)
2. For ____ sets of observations, the observed percentage error is____________________

Precautions:

1. Pulleys should be smooth.
2. Place the weights gently
3. Fix the drawing Sheet properly.

Viva Questions:

1. Describe the law of triangle of forces?

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Q.-2. State Lami's theorem?

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Q.-3. What are the analytical and graphical equilibrium conditions?

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Q.-4. What are the limitations of Lami`s theorem?

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Q.-5. What is the exact no. of forces for which Lami`s theorem is applied?

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