CAIE A-Level Physics AS 4.2.1 The Principle of Moments Questions
Apply the principle of moments to calculate unknown forces, distances and moments about a pivot.
- Syllabus
- 2028–2030
- Course
- Physics 9702
- Level
- AS
Apply the principle of moments to calculate unknown forces, distances and moments about a pivot.
A thin disc of radius r is supported at its centre O by a pin. The disc is supported so that it is vertical. Three forces act in the plane of the disc, as shown in Fig.2.1.
Fig. 2.1
Two horizontal and opposite forces, each of magnitude 1.2 N , act at points A and B on the edge of the disc. A force of 6.0 N , at an angle θ below the horizontal, acts on the midpoint C of a radial line of the disc, as shown in Fig. 2.1. The disc has negligible weight and is in equilibrium.
Friction between the disc and the pin is negligible.
Determine the angle θ.
θ=∘
(anticlockwise moment = ) 6.0×r/2×sinθ6.0×r/2×sinθ=2.4rθ=53∘