Torque

1
Torque
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Center of Gravity

• The point at which all the weight is considered
  to be concentrated
• The point at which an object can be lifted w/o
  producing rotation

3
Center of Gravity

• In asymmetric objects, the center of gravity may
  not be the geometric center

4
Translational Equilibrium

• Occurs when an object is not accelerating

5
Rotational Equilibrium

• Occurs when an object is not rotating or the
  rotation is uniform

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Torque

• The rotational effect of an object produced by a
  net force that is not applied to the center of
  gravity

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FT
Torque arm
Torque arm
A
B
C
C Pivot Point or Center of rotation
WA
WB
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Pivot Point

• Reference point from which to measure rotational
  forces

9
Torque Arm

• The length between the pivot point and the point
  where a force is applied

10
Torque

• The product of the applied force and the length
  of its torque arm

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FT
Torque arm
Torque arm
6 m
A
4 m
B
C
TorqueA WA x 6 m TorqueB WB x 4 m
WA
WB
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FT
B
Torque Arm A
b
a
WB
Torque Arm B
A
TorqueA WAAcosa TorqueB WBBcosb
WA
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FN FA sin a
FN
FA
a
a
l sin a
Torque FAl sin a
14
Calculate the torque on a 250 cm rod with a pivot
point at one end and a 500.0 g object sitting on
the other end
15
A person ties a rope to one end of a 10.0 m
I-beam tries lift it by pulling with 2500 N at
37o from horizontal