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Predict the readings on the scales: 0 30 ? 0 10 30 20 ? 20 1.0 m 0.5m Mbar = 1.0 kg 1.0 kg 10 Predict the readings on the scales: 0 30 0 10 20 10 N 30 20 1.0 m 0.5m Mbar = 1.0 kg 10 1.0 kg 10 N Now predict the readings: 0 30 ? 0 10 30 20 20 1.0 m 0.8m Mbar = 1.0 kg a=0 ? 1.0 kg 10 Which force is most effective in causing rotation? F2 standard meter stick F1 standard pivot point standard frictionless pond Now which force is most effective in causing rotation? F2 standard meter stick F1 standard pivot point standard frictionless pond Definition of torque t = rFperp In practice…. F = 200 N t = r F = (3 m)(200 N) = 600 m - N r=3m Pivot Useful force method: only the component Fperp causes torque. F q q F sin q r t = r (F sin q) = r Fperp Fixed Pivot Point Torque • A torque is produced when a force is applied with “leverage”. • net torque causes angular acceleration • Only the perpendicular force contributes to the Torque. Torque • net torque causes angular acceleration if the force is applied “off center” • If net torque = 0, angular velocity() = constant. • Doubling the net torque doubles angular acceleration (). Let’s practice: 0 30 ? 10 20 pivot 1.0 m 200 N 200 N Let’s practice: 0 30 ? 10 400 N 20 pivot 1.0 m 0.5m 200 N Linear equilibrium: a=0 Fleft = Fright 100 N ??? N 150 N Rotational equilibrium =0 0 30 ? 10 800 N 20 t1 = t2 pivot 1.0 m 0.25m 200 N Let’s solve the problem: 0 30 ? 0 10 30 20 ? 20 1.0 m 0.8m Mbar = 1.0 kg a=0 =0 Fnet = 0 tnet = 0 1.0 kg 10 t1 = t2 (10 N)(.5 m) + (10 N)(.8 m) = TR(1 m) TL = 7 N TR = 13 N TL 0.8m Pivot 0.5m 10 N 10 N TR Let’s solve the problem: 0 30 ? 0 10 30 20 ? 20 1.0 m 0.6m Mbar = 1.0 kg a=0 =0 Fnet = 0 tnet = 0 1.0 kg 10