. Practical physics. 64 FORCE AND MOTION 82. Component of gravity effective in producing the motionof the pendulum. When a pendulum is drawai aside from itsposition of rest (Fig. 65), the force acting on the bob is itsweight, and the direction of this force is vertical. Let it berepresented by the line OB. Thecomponent of this force in thedirection in which the bob is freeto move is On, and the componentat right angles to this direction isOm. The second component Omsimply produces stretch in thestring and pressure upon the pointof suspension. The first compo-nent On is alone responsible forthe
. Practical physics. 64 FORCE AND MOTION 82. Component of gravity effective in producing the motionof the pendulum. When a pendulum is drawai aside from itsposition of rest (Fig. 65), the force acting on the bob is itsweight, and the direction of this force is vertical. Let it berepresented by the line OB. Thecomponent of this force in thedirection in which the bob is freeto move is On, and the componentat right angles to this direction isOm. The second component Omsimply produces stretch in thestring and pressure upon the pointof suspension. The first compo-nent On is alone responsible forthe motion of the bob. A consid-eration of the figure shows thatthis component becomes largerand larger the greater the dis-placement of the bob. When thebob is directly beneath the point of support, the componentproducing motion is zero. Hence a pendulum can be per-manently at rest only when its bob is directly beneath thepoint of suspension.*. Fig. 65. Force acting on dis-placed pendulum QUESTIONS AND PROBLEMS 1. The engines of a steamer can drive it 12 mi. per hour. How fastcan it go up a stream in which the current is 3 mi. })er hour ? How fastcan it come down the same stream ? 2. The wind drives a steamer east with a force which would carry it12 mi. per hour, and its propeller is driving it south with a force whichwould carry it 15 mi. per hour. What distance will it actually travel inan hour ? Draw a diagram to represent the exact path. * It is reconniiended that the study of the laws of the pendulum be intro-duced into the laboratory work at about this point (see Experiment 12,authors Manual). COMPOSITION AND RESOLUTION OF FORCES 65
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectphysics, bookyear1922
