mechanical advantage. what does it mean to be in rotational equilibrium? all torques are balanced...
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Mechanical Advantage
What does it mean to be in rotational equilibrium?
•All torques are balanced•The lever is not rotating
If in rotational equilibrium:
EEE dFT LLL dFT
L
E
E
L
EELL
EL
d
d
F
F
dFdF
TT
Mechanical Advantage
•A measure of how much easier the machine makes a task
•Ratio of output force to input force•Known as force amplification
Ideal Mechanical Advantage (IMA)•The mechanical advantage the machine
will provide if all conditions are perfect •No friction, no wear, all forces applied in
the proper directions
L
E
d
dIMA
Actual Mechanical Advantage (AMA)
•The mechanical advantage the machine provides when used
•Forces are measured
E
L
F
FAMA
•If the force is transmitted perfectly (100% efficient)
If the force is not transmitted perfectly
IMAAMA
d
d
F
F
L
E
E
L
IMAAMA
d
d
F
F
L
E
E
L
•Copy Table 1 from Pg 88 in text
IMA - Pulley
•IMA of a pulley is based on the number of strands supporting the mass
% Efficiency
%100% xIMA
AMAEfficiency
How effective a machine is at transforming an input into an output
Example 1:
The following pulley system carries a mass of 30.0kg.
Calculate:1) Actual Mechanical
Advantage2) Ideal Mechanical
Advantage3) % Efficiency
FE= 100N
Example 2:A pulley system has a 20.0kg load attached
to it. The load arm is 50.0cm, the effort arm is 200cm and the effort force is 60N.
Calculate:a) FL
b) AMAc) IMAd) % Efficiency
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