11Starting Rotation of Object lever armperpendicular distance from the axis of rotation to the point where the force is exertedL= rsinθθ=angle at which the force is applied!!!r=distance to point where force is applied to axis
12Torquemeasure of how effectively a force causes rotationN*mτ (tau)
13Practice ProblemHow much torque is applied if a wrench applies a force of 240N at an angle of 60.0° from the perpendicular? The wrench is 32cm long.
14Net TorqueNet=Sumdecide on a positive & a negative rotation direction∑τ=τ1+τ2
15Practice ProblemAshok, whose mass is 43kg, sits 1.8m from the center of a seesaw. Steve, whose moss is 52 kg, wants to balance Ashok. How far from the center of the seesaw should Steve sit?
19Practice ProblemWhat is the moment of inertia of a hockey puck that has a mass of 170g, a thickness of 2.5 cm, and a diameter of 7.6 cm? The formula for the moment of inertia of a cylinder is I=1/2mr2.
21Newton’s Second Law of Rotation Replace Newton’s Second Law (F=ma) with angular termsa=αF=τnetm=I
22Practice ProblemA solid steel wheel has a mass of 15kg and a diameter of 0.44m. It starts at rest. You want to make it rotate at 8.0 rev/s in 15s.What torque must be applied to the wheel?If you apply the torque by wrapping a strap around the outside of the wheel, how much force should you exert on the strap?If the force on the strap were twice as great, what would be the speed of rotation of the wheel after 15s?
24Center of Massthe point on the object that moves in the same way that a point particle would moveLocatingSuspend the object from a point, center of mass is along the vertical line drawnintersection of 2 vertical lines will give a pointCenter of mass for a persondifferent male & female
25Center of Mass and Stability Stablean external force is required to tip objectHigher center of gravityless force needed to upsetEquilibriumtranslational equilibriumrotational equilibrium
26Practice ProblemA 5.8kg ladder, 1.80m long, rests on two sawhorses. Sawhorse A is 0.60m from one end of the ladder, and sawhorse B is 0.15m from the other end of the ladder. What force does each sawhorse exert?What if the mass of the ladder is 11.4kg?