Forces of 4N and 20N act on the ends of the lever. The length of the lever is 60 cm.

| July 14, 2021 | education

Forces of 4N and 20N act on the ends of the lever. The length of the lever is 60 cm. Where is the fulcrum if the lever is in equilibrium

F1 = 4 N.

F2 = 20 N.

L = 60 cm = 0.6 m.

r1 -?

r2 -?

When the lever is in equilibrium, the moments of forces that act from different sides of the lever are equal to each other: M1 = M2.

The moment of force M is the product of the force F by the smallest distance from the point of application of the force to the axis of rotation: M = F * r.

F1 * r1 = F2 * r2.

r1 + r2 = L.

r2 = L – r1.

F1 * r1 = F2 * (L – r1).

F1 * r1 = F2 * L – F2 * r1.

F1 * r1 + F2 * r1 = F2 * L.

r1 = F2 * L / (F1 + F2).

r1 = 20 N * 0.6 m / (4 N + 20 N) = 0.5 m.

r2 = 0.6 m – 0.5 m = 0.1 m.

Answer: the fulcrum is at a distance r1 = 0.5 m from the application of the force F1, and at a distance r2 = 0.1 m from the application of the force F2.



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