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Transcript
Consider a meter stick of mass 0.306 kg pivoted at one end which is held horizontally by a vertical string. a. Draw an extended force diagram of the meter stick. Fg What forces act upon the meter stick? Where should the force of gravity be considered to act? Center of Gravity – the single point on a body where the force of gravity effectively acts. As long as the local gravitational field strength (g) is essentially constant, the center of gravity is the same as the center of mass. Consider a meter stick of mass 0.306 kg pivoted at one end which is held horizontally by a vertical string. a. Draw an extended force diagram of the meter stick. FT FN Fg Do all three force exert torques around the pivot? The Normal Force does not exert a torque because it acts radially (through the axis of rotation)! Consider a meter stick of mass 0.306 kg pivoted at one end which is held horizontally by a vertical string. b. Complete the torque bar graph quantitatively. FT FN N g T net Fg g r Fg g r mg 0 g 0.50 m0.306 kg 9.8 N kg g 1.5 Nm -1.5 Nm Consider a meter stick of mass 0.306 kg pivoted at one end which is held horizontally by a vertical string. b. Complete the torque bar graph quantitatively. FT FN 1.5 Nm N g T net Fg Since the angular velocity of the meter stick doesn’t change, the torques must be balanced! 0 net ?0 Newton’s First Law! -1.5 Nm Consider a meter stick of mass 0.306 kg pivoted at one end which is held horizontally by a vertical string. c. What is the tension in the string? FT FN 1.5 Nm N g T net Fg T 1.5 Nm r FT 1.5 Nm 0 -1.5 Nm 1.5 Nm FT r 1.5 Nm FT 1.0 m FT 1.5 N Consider a meter stick of mass 0.25 kg pivoted at one end which is held horizontally by a vertical string. Equilibrium Occurs when F 0, 0 FT FN Static Equilibrium Occurs when F 0, 0, and v 0 Fg FN FT Fg Since v constant FN Fg FT FN mg FT FN 0.306 kg 9.8 N 1.5 N kg 3.0 N FN 1.5 N
