1. Name ________________________________ Physical Science
Date _______________ Period ________ Mrs. Haentges
Notes for Chapter 6 – Work and Machines
 Work - _____energy transferred when forces make something move______
In order for work to be done, something must ____move____
Formula for work:
Work = ______force______ x _____distance_____
W = f  d
Unit for work ____Joule____________

2. Example #1:
A force of 75 N is used to move a couch 3 m. How much work is done in moving the couch?
  W = f●d
W = 75 N ● 3 m
  W = 225 J
Example #2:
A lawn mower is pushed with a force of 80 N. If 12,000 J of work is done in mowing a lawn, what is the total distance the lawn mower was pushed?
d = W/f
d = 12,000 J/80 N
d = 150 m

3. Power - __amount of work done in a second__(rate at which work is done)__
Formula for power:
Power = work P = w (f●d)
time t t
(sometimes you will need to calculate work first)
Unit for power ______watt_______
Example #1:
A runner performs 1300 J of work in 10 seconds. What is the runner’s power?
  P = w/t
P = 1300J/10 s
P = 130 W 
How could the runner be more powerful? _____run faster______

4. Machine - _____device that makes doing work easier_________
Three ways that machines make work easier:
● increasing force applied to the object
● increasing the distance over which the force is applied
● changing the direction of the force
Input force - ____force applied TO the machine________
Example of input force - ____pulling down on a crowbar______
Output force - _____force applied BY the machine_______
Example of output force - ___crowbar lifting up a lid_____
Ideal Machine - ____has no friction___(work in = work out)___

5. Mechanical Advantage - ____the ratio of output force to_______
___input force__(how many times easier it is to use the machine)__
Formula for mechanical advantage:
Mechanical advantage = output force
  input force
MA = Fout
  Fin
Mechanical advantage does not have a label.

6. Example #1:
A worker applies an input force of 20 N to pry open a window that has an output force of 500 N. What is the mechanical advantage of the crowbar?
  MA = Fout/Fin
MA = 500 N/20 N
  MA = 25
Example #2:
Find the input force needed to lift a 200 N rock, using a jack with a mechanical advantage of 10.
  Fin = Fout/MA
Fin = 200 N/10
Fin = 20 N

7. Efficiency - __how much work put into a machine is____________
____changed to useful work put out by a machine_____________
The Wout of a machine is less than the Win because of __friction___
Therefore, machines are always less than 100% efficient.
How do you increase the efficiency of a machine?
decrease the friction

8. Simple Machine - ____does work with only one movement_________
Examples of simple machines - ______________________________
_______________________________________________________
Six types of simple machines
1. Levers
2. Pulleys
3. Wheel and Axle (gear)
4. Inclined Plane
5. Screw
6. Wedge

9. 1. Levers - _bar that is free to pivot around a fixed point_________
Parts: fulcrum - ___fixed point of a lever_______________
Input arm - __where the input force is applied______
Output arm - __where the output force is applied____
1st class lever – fulcrum is located between the input and output forces
example – seesaw, screwdriver opening a can
  O I
  Δ-F

10. 2nd class lever – output force is located between the input force and the fulcrum
example - wheelbarrow
O I
Δ-F
3rd class lever – input force is located between the output force and the fulcrum
example – baseball bat, rake
  O I___________
  Δ-F
IMA of a lever = length of input arm or Lin
length of output arm Lout

11. 2. Pulleys - ___grooved wheel with a rope running along the groove____
Example: on a flagpole or a crane
Pulleys work like ____first class levers______________________
The IMA of a single fixed pulley is ____1____
Block and tackle – ____system of pulleys_______
More pulleys give greater mechanical advantage – less effort.
The IMA of a block and tackle = ____number of pulleys_____

12. 3. Wheel and Axle - __an axle attached to the center of a ______
____wheel – the wheel and axle rotate together_______________
examples: doorknob, screwdriver
The IMA of a wheel and axle = radius of wheel or rw
radius of axle ra
Gears - _____a wheel and axle with teeth around the wheel________
A gear is a _____ modified wheel and axle_______
A large gear pushes a small gear

13. 4. Inclined Plane - ___a sloping surface used to raise objects_______
The amount of work done on moving an object is the same
whether you lift the object straight up or slide it up a ramp. Why? Work = _____force_____ X ____distance_____
When you lift the object, the force is ______large____
but the distance is ____small____ If you use a ramp, the
distance is ____large______ but you use ___less____ force.
IMA of inclined plane = length of slope or Lslope
height of slope Hslope

14. 5. Screw - _____inclined plane wrapped around a cylindrical post_______
The threads form a tiny ramp that runs from the tip to the top.
6. Wedge - _____inclined plane with one or two sloping sides_____
_____that changes the direction of the input force______________
example: knife , ax blade

15. Compound machines - ____two or more simple machines______
_____that work together_________________________________