MACHINES and EFFICIENCY - PowerPoint PPT Presentation

Loading...

PPT – MACHINES and EFFICIENCY PowerPoint presentation | free to download - id: 7bbbd4-NmViN



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

MACHINES and EFFICIENCY

Description:

... A machine composed of two or more simple machines Key ... Machines PowerPoint Presentation PowerPoint Presentation Three Classes of Levers Three ... – PowerPoint PPT presentation

Number of Views:50
Avg rating:3.0/5.0
Slides: 28
Provided by: FortT89
Learn more at: http://www.fortthomas.kyschools.us
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: MACHINES and EFFICIENCY


1
MACHINES and EFFICIENCY
  • Chapter 9.8-9.9

2
Key Terms
  • Work Force x distance
  • Simple machine
  • a device used to multiply forces or change the
    direction of forces
  • Compound machine
  • A machine composed of two or more simple machines

3
Key Terms
  • Input (effort)
  • Input distance the distance you input the force
    when using a machine
  • Input force the force you use when using a
    machine
  • Output (resistance)
  • Output distance the distance the object that
    work is done on moves
  • Output force the force required to move the
    object without a machine (usually the weight of
    the object in newtons)

4
Key Terms
  • Mechanical Advantage (MA)
  • A unitless ratio that indicates the number of
    times a machine multiplies your input force
  • Ideal Mechanical Advantage (IMA)
  • The calculated MA, does not consider friction
  • Actual Mechanical Advantage (AMA)
  • The measured or real MA, does consider friction
  • Because of friction, AMA lt IMA

5
A simple machine
  • Multiplies and redirects force
  • Does not reduce the amount of work to be done,
    but makes work easier.
  • MA gt 1 means that your input force will be less
    than your output force
  • More leverage means more mechanical advantage
  • If you increase MA, then
  • Input force will decrease
  • Input distance will increase

6
Key Terms
  • Efficiency (a ratio)
  • Is calculated using the following equations
  • Actual mechanical advantage/idealized mechanical
    advantage
  • Useful work output/total work input

7
Key Terms
  • Efficiency of a machine decreases as friction
    increases
  • Friction increases the thermal energy by
    increasing molecular KE (non-mechanical energy)
  • In other words friction causes the particles to
    speed up, raising the average KE of the particles
    (and temperature!)
  • Friction causes the useful work output to be less
    than the total work input

8
Key Terms
  • When using a machine
  • Work is done to move the object
  • Work is done against friction
  • Useful work output is the work done to move the
    object
  • Total work input is work done to move object
    work done against friction

9
Simple Machines
  • Two families

Lever
Inclined plane
--Lever --Pulley --Wheel and axle
--Ramp --Wedge --Screw
10
LEVER FAMILY
11
The Lever
fulcrum
12
Three Classes of Levers
  • First class

Examples Crowbar See-saw
13
Three Classes of Lever
  • Second class

Examples Wheelbarrow Door
14
Three Classes of Lever
  • Third class

Examples Human arm Baseball bat
15
Calculating the Mechanical Advantage of a Lever
  • MA input distance/output distance which is MA
    length of effort arm/length of resistance arm.

Effort or input distance
0.5 m
Resistance or output distance
2.5 m
Effort arm
Resistance arm
16
Calculating the Mechanical Advantage of a Lever
  • 2nd class lever
  • 3rd class lever

2nd class levers decrease the input force but
increase the input distance.
3rd class levers reduce the output force, but
increase output distance and speed
17
  • Which lever would have the highest mechanical
    advantage and why?

b has the largest input distance, giving the
largest MA
c
b
a
18
Pulley
Fixed pulley 1 support rope IMA 1
19
Pulleys
IMA 2
Two supporting ropes
20
Pulleys
IMA ?
2
21
Pulley
How many support ropes?
4
What is the IMA?
4
22
Wheel and Axle
  • Wheel connected to a shaft

GIVES YOU LEVERAGE
23
INCLINED PLANE FAMILY
24
Inclined planes
  • Ramps

25
Wedge
  • Two inclined planes stuck together

26
Screw
  • An inclined plane wrapped around a cylinder

27
What type of machine is this?
Compound made of two or more machines
Two 1st class levers
About PowerShow.com