Simple Machines By Nathan. Contents Pulley Wedge Lever Inclined Plane Wheel and Axle Gears Screw.
MachinesMachines II. The Simple Machines Lever Pulley Wheel & Axle Inclined Plane Screw Wedge.
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Transcript of MachinesMachines II. The Simple Machines Lever Pulley Wheel & Axle Inclined Plane Screw Wedge.
![Page 1: MachinesMachines II. The Simple Machines Lever Pulley Wheel & Axle Inclined Plane Screw Wedge.](https://reader035.fdocuments.us/reader035/viewer/2022062322/5697c0301a28abf838cda924/html5/thumbnails/1.jpg)
Machines Machines Machines Machines II. The Simple Machines
Lever Pulley Wheel & Axle
Inclined Plane Screw Wedge
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A. LeverLever
a bar that is free to pivot about a fixed point, or fulcrum
“Give me a place to stand and I will move the Earth.”
– Archimedes
Engraving from Mechanics Magazine, London, 1824
Effort arm
Resistancearm
Fulcrum
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A. Lever Ideal Mechanical Advantage (IMA)
frictionless machine
r
e
L
LIMA
Effort arm length
Resistancearm length
Le must be greater than Lr in order to multiply the force.
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A. LeverFirst Class Lever
can increase force, distance, or neither
changes direction of force
r
e
L
LIMA
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A. LeverSecond Class Lever
always increases force
r
e
L
LIMA
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A. LeverThird Class Levers
always increases distance
r
e
L
LIMA
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B. PulleyPulley
grooved wheel with a rope or chain running along the groove
a “flexible first-class lever”
LeLr
F
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B. Pulley Ideal Mechanical Advantage (IMA)
equal to the number of supporting ropes
IMA = 0 IMA = 1 IMA = 2
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B. PulleyFixed Pulley
IMA = 1
does not increase force
changes direction of force
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B. PulleyMovable Pulley
IMA = 2 increases forcedoesn’t change direction
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B. PulleyBlock & Tackle
combination of fixed & movable pulleys increases force (IMA = 4) may or may not change direction
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C. Wheel and AxleWheel and Axle
two wheels of different sizes that rotate together
a pair of “rotatinglevers”
Wheel
Axle
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C. Wheel and Axle Ideal Mechanical Advantage (IMA)
effort force is usu. applied to wheel
axle moves less distance but with greater force
r
e
r
rIMA
effort radius
resistance radius
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Problems You use a 160 cm plank to lift a large
rock. If the rock is 20 cm from the fulcrum, what is the plank’s IMA?
GIVEN:
Lr = 20 cm
Le = 140 cm
IMA = ?
WORK:
IMA = Le ÷ Lr
IMA = (140 cm) ÷ (20 cm)
IMA = 7
IMA
Le
Lr
20cm
160cm
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Problems A crank on a pasta maker has a radius
of 20 cm. The turning shaft has a radius of 5 cm. What is the IMA of this wheel and axle?
GIVEN:
re = 20 cm
rr = 5 cm
IMA = ?
WORK:
IMA = re ÷ rr
IMA = (20 cm) ÷ (5 cm)
IMA = 4
IMA
re
rr
5 cm 20 cm
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Problems A steering wheel requires a mechanical
advantage of 6. What radius does the wheel need to have if the steering column has a radius of 4 cm?
GIVEN:
IMA = 6
re = ?
rr = 4 cm
WORK:
re = IMA · rr
re = (6)(4 cm)
re = 24 cm
IMA
re
rr
rr re
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Problems You need to lift a 150 N box using only
15 N of force. How long does the lever need to be if the resistance arm is 0.3m?
GIVEN:
Fr = 150 N
Fe = 15 N
Lr = 0.3 m
Le = ?
MA = 10
WORK:
Le = IMA · Lr
Le = (10)(0.3)
Le = 3 m
Total length = Le + Lr
Total length = 3.3 m IMA
Le
Lr
0.3m
?
150N
15N