CHAPTER 8 MACHINES
description
Transcript of CHAPTER 8 MACHINES
![Page 1: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/1.jpg)
CHAPTER 8MACHINES
![Page 2: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/2.jpg)
•Machines make work easier by changing the force you exert insize or direction, or both.•But it does not change the amount of work done. •A machine is a device that makes work easier.
![Page 3: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/3.jpg)
Types of Machines
• Lever
• Inclined Plane
• Pulley
• Wheel and Axle
• Wedge
• Screw
![Page 4: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/4.jpg)
SIMPLE MACHINES
Do work
with one
movement
COMPOUND MACHINES
Are a combination
of two or more simple machines.
![Page 5: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/5.jpg)
MACHINES
SIMPLE MACHINES
INCLINED PLANETYPE
LEVER TYPE
•Inclined Plane•Screw•Wedge
•Lever•Wheel & Axle•Pulley
COMPOUND MACHINE
AXE
Wedge and
Lever
![Page 6: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/6.jpg)
EFFORT FORCE (Fe) is the force you exert on a machine*
RESISTANCE FORCE (Fr) is the force applied by the machine to overcome resistance.*
EFFORT DISTANCE (de) is the distance moved by the effort force.*
RESISTANCE DISTANCE (dr) is the distance moved by the resistance force.
![Page 7: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/7.jpg)
WORK INPUT (Win) is the work put into the machine
eein dFW
WORK OUTPUT (Wout) is the work that the machine puts out.
rrout dFW
![Page 8: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/8.jpg)
IDEAL MACHINE
rree
outin
dFdF
WW
![Page 9: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/9.jpg)
MECHANICAL ADVANTAGE (MA) is the number of times a machine multiplies the effort force.
e
r
FF
MA
IDEAL MECHANICAL ADVANTAGE (IMA)
r
e
dd
IMA
![Page 10: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/10.jpg)
EFFICIENCY
%100
%100
ee
rr
in
out
dF
dF
W
WEfficiency
An ideal machine has an efficiency of 100%. Machines have efficiency of < 100%
![Page 11: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/11.jpg)
Machines make work easier by changing the force you exert in size and/or direction.
![Page 12: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/12.jpg)
LEVERSA lever is a bar that is free to pivot, or turn, about a fixed point.The fixed point of a lever is called the fulcrum. EFFORT FORCE
FULCRUMRESISTANCE
FORCE
![Page 13: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/13.jpg)
LEVERSThe part of the lever on which the effort force is applied is called the effort arm.The part of the lever that exerts the resistance force is called the resistance arm.
RESISTANCE ARM
EFFORT ARM
![Page 14: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/14.jpg)
LEVERS
RESISTANCE ARM
EFFORT ARM
Arm Resistance ofLength
armeffort ofLength
r
e
d
dIMA
![Page 15: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/15.jpg)
FIRST CLASS LEVER
The fulcrum is always in between the effort force and the resistance force. Examples: seesaw, hammer, hair clip, bottle opener, crow bar and cart
![Page 16: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/16.jpg)
FIRST CLASS LEVER
RESISTANCEARM
EFFORT ARM
EFFORT FORCE
RESISTANCE FORCE
![Page 17: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/17.jpg)
SECOND CLASS LEVERThe resistance is located between the effort force and the fulcrum. They always multiply effort force. Examples: nutcracker, wheelbarrow, hole puncher,bottle opener, lemon squeezer
![Page 18: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/18.jpg)
SECOND CLASS LEVER
RESISTANCE ARM
EFFORT ARM
EFFORT FORCE
RESISTANCE FORCE
![Page 19: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/19.jpg)
THIRD CLASS LEVERThe effort is located between the resistance force and the fulcrum. They do not multiply effort force. Examples: rake, broom,fishing pole, your arm, andhockey stick
![Page 20: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/20.jpg)
THIRD CLASS LEVER
RESISTANCE ARM
EFFORT ARM
EFFORT FORCE
RESISTANCE FORCE
![Page 21: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/21.jpg)
THIRD CLASS LEVER
RESISTANCE ARM
EFFORT ARM
EFFORT FORCE
RESISTANCE FORCE
Effort arm is always shorter than the resistance arm, so it cannot multiply force. It’s MA isalways less than 1.
![Page 22: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/22.jpg)
LEVERS WITH A HUMAN TOUCH
Your neck muscles support the effort force to hold up the resistance weight of your head.
First Class Lever
Tip of your feet-FulcrumWeight -ResistanceMuscles- Effort
Second Class Lever
![Page 23: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/23.jpg)
LEVERS WITH A HUMAN TOUCH
Elbow-FulcrumBiceps-EffortWeight-resistance
Third Class Lever
RF
E
![Page 24: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/24.jpg)
PROBLEM #1
A lever uses a force of 250 N to move a rock that weighs 3000 N. Find the mechanical advantage of using the lever.
12250
3000
N
N
F
FMA
e
r
![Page 25: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/25.jpg)
A simple machine allows a worker to move an effort distance 45 cm in order to move a resistance distance 20 cm. What is the ideal mechanical advantage of the machine?
PROBLEM #3
25.220
45
r
e
d
dIMA
![Page 26: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/26.jpg)
PULLYING WITH PULLEYSA pulley is a grooved wheel with a rope or a chain running along the groove. A pulley works something like a first class lever. Instead of a bar a pulley has a rope. The axle of the
pulley acts like the fulcrum. The two sides of the pulleyare the effort arm and the resistancearm.
![Page 27: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/27.jpg)
SINGLE FIXED PULLEY•It is lifted the same distance as it is pulled at the other end of the rope.•Example: flagpole, blinds.•Force is not multiplied. There is only a change in the direction of the force applied.
W F
![Page 28: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/28.jpg)
SINGLE MOVABLE PULLEYS
•Force is multiplied.IMA = 2, since two wires are supporting the resistance. The effort distance must be twice as large as the resistance distance. Example:construction cranes.
W
F
![Page 29: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/29.jpg)
BLOCK AND TACKLE
•It is combination of fixed and movable pulley.•It can produce large enough force to lift automobiles.
![Page 30: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/30.jpg)
Wheel and axle is a simple machine consistingof two wheels of different sizes that rotate together.
Examples: doorknob, faucets, handles, steering wheel of a car etc.
An effort force is applied to the larger wheel. The smaller wheel, called the axle, exerts the resistance force.
It allows us to use less force to do work.
WHEEL AND AXLE
![Page 31: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/31.jpg)
Axleof Radius Wheelof RadiusIMA
Gear is a modified wheel and axle machine. It is wheel with teeth along its circumference. Effort is exerted on one of the gears and the other gear turns.
WHEEL AND AXLE
![Page 32: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/32.jpg)
Slanting boards and ramps are called inclined planes. They are sloping surfaces used to raise objects. W=weight, H=height, L=length, F=force
F
W
H
L
INCLINED PLANE
![Page 33: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/33.jpg)
F
W
H
L
HLIMA
FWMA
HWW
LFW
out
in
%100
%100
LFHW
WW
Efficiencyin
out
![Page 34: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/34.jpg)
What is the ideal mechanical advantage of a ramp 4 cm long and 2 cm high?
22
4
H
LIMA
PROBLEM #5
![Page 35: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/35.jpg)
What is the efficiency of a machine with work input 1000 J and work output 700 J?
%%xJ
Jefficiency
%xWin
Woutefficiency
701001000
700
100
PROBLEM #8
![Page 36: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/36.jpg)
Screw is another form of inclined plane. The threads form a tiny ramp that runs from its tip to near its top. As you turn the screw, the threads seem to pull the screw into the wood.
SCREWS
![Page 37: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/37.jpg)
When a screw is turned ,it moves forward. At the same time, it presses against the material around it. Many turns are needed to move the screw a short distance. But the screw produces a far greater force than the force needed to turn it.
SCREWS
![Page 38: CHAPTER 8 MACHINES](https://reader035.fdocuments.in/reader035/viewer/2022081420/56813c47550346895da5c4e1/html5/thumbnails/38.jpg)
Wedge is a form of inclined plane. It is a moving inclined plane. The material remains in one place while the wedge moves through it.Examples: blade of an axe, knife blade, razor blade, door stop, chisel.
WEDGE