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12-Apr-2017
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### Transcript of Torque,stability and equilibrium

• *door top viewF1F2axis of rotationr1r2Where:F = forcer = lever arm= perpendicular distance from the axis of rotation to the line along which the forces acts.here., F

• *door top viewF1F2axis of rotationr1r2 F x r

Moment of Force or Torque ()

• a vector quantity that determines the ability of a force to introduce rotation. = rF ; unit: mNMagnitude of the applied forceDistance from point of application to pivot (location of applied force)Angle ( direction of the applied force)

• F1F2F3r1r2 F1 > F2 F2 < F1 = 0NOTE: in general = rFRemind us that we must use the distance from the axis of rotation that is perpendicular to the line of action of the forcer = r sin

• F2 = rFl = rF sinWe can use = r F or = r F or = r F sin to calculate the torque whichever is easiest.Line of action of a force - the line of motion of a

force is an imaginary line of indefinite length drawn a long the direction of the forceThe moment arm is the perpendicular distance

from the line of action of a force to the axis of rotation.

• 1. An 80 N acts at the end of a 12 cm wrench as shown. Find the torque.80 N12 cm =60o 2. Find the resultant torque about axis A for the arrangement shown:

=30o =30o 4 m2 m6 mF3 = 20 NF2 = 40NF1 = 30 N

• Torque is a vector quantity that has a direction as well as magnitude

Thumb F (force)Pointer r (moment arm)Middle finger direction of (torque)

• Up+Down-Right+left-Outward+Inward-CCCounterclockwise+Cclockwise-

• Car at rest

Constant speed, no change in direction

• wheel at restConstant rotation

• The center of mass lies at the geometric center for a symmetric, uniform density object.

h/3h

Rh/2h

h/2h

• The center of mass can be outside the mass of the body.

Center of mass

• Ability of an object to return to its original position after it is displaced or tilted slightly- CG is below of point of support- the objects return to its original position- When object is displaced, the object moves even farther from its position- When object is displaced, the object remain in its position

• cm