1. Chapter 5.2 Physical Science WZPP ps Ok web post
Using Machines
Chapter 5.2
Physical Science
WZPP ps
Ok web post

2. What is a Machine? Something that makes work (force x distance) easier
Does not need to be powered
Can be powered by the force of a person

3. Making work easier Increasing the force applied to an object or
You can do the same amount of work by applying a small force over a greater distance or
a large force over a short distance
See the jack example:
figure 6, page 132

4. Making work easier Increasing the distance Work stays the same
When you increase the distance, less force will be needed

5. Making work easier Changing Directions
This can be to the sides or opposite direction

6. Work Done by Machines
Two kinds of forces need to be considered when using machines
Work I do on the machine (Win)
Work done by the machine (Wout)

7. Conserving Energy
Amount of energy put in the machine needs to be greater than the energy out of the machine
This is real life
Machines can not create energy
Some energy is lost as friction

8. Ideal Machine Is a perfect machine No friction, no mass, no weightSo
Win = Wout (remember, F x D = W)
(Effort Force x Effort Distance = Resistance force x resistance distance)
Fe x De = Fr x Dr
5.2B ws

9. Mechanical Advantage (MA)
Is the number of times a machine multiples an effort force
Mechanical advantage = resistance force divided by the Effort force
M A = Fr / Fe

10. Efficiency
Is the measure of how much work put into a machine is changed into useful work by the machine
High efficiency machines produce less heat from friction
Efficiency is Wout / Win x 100%

11. Efficiency Efficiency of real machines is always less than 100%
Machine can be made more efficient by reducing friction
Add lubricant– oil, grease
end notes 5.2 ps 5.2C ws