1. Machines: Making Work Easier

2. I. What is a Machine?
A. A machine is a device that makes doing work easier.
B. Machines increase work by:
1. Increase force applied
Ex. Screw driver
2. Increasing distance the force is applied to
Ex. Rake
3. Changing the direction of an applied force
Ex. Pulley

3. II. Work = Force x Distance
A. The amount of work done is the product of the amount of force & distance covered.
1. Machines allow for work to change how force is applied.
B. The work done will always be equal if the force applied is lessened while the distance the force is exerted increases.
Ex. Lifting heavy furniture vs. sliding it up a ramp.

4. III. Changing Direction
A. Some machines can change the direction of the force applied.
1. The force exerted downward can cause an upward change
Ex. Car jack, wood axe , crowbar

5. IV. Input vs. Output Forces
A. Two forces are involved when a machine is used to do work.
1. Force applied to the machine is the applied force;
work put into machine is input work (Fin Win)
2. Force applied by the machine is the output force;
work done by machine is output work (Fout Wout)
Fin Win = FoutWout

6. V. Conserving Energy
A. Energy can not be created or destroyed only transferred so therefore the amount of energy the machine transfers can not be greater than the amount of energy you put into the machine.
The input work will always be greater since some energy is lost as thermal energy due to friction unless a perfect machine is created

7. VI. Mechanical Advantage & Efficiency
A. The ratios of output force to input force is equal to the mechanical advantage of a machine (MA)
B. Equation: MA = output force / input force
C. Some energy is always lost as thermal energy to see how much work put into a machine is useful we measure efficiency.
Efficiency (%) = output work / input work x 100%

8. Simple Machines

9. I. What is a simple machine?
A. Simple machine is a machine that does work with only one movement of the machine
B. There are 6 types of simple machines:
1. Lever
2. Pulley
3. Wheel & Axle
4. Inclined Plane
5. Screw
6. Wedge

10. 1. Lever a. a bar that is free to pivot or turn around a fixed point.
1. The fix point is called the fulcrum
b. There are 3 classes of levers based on the location of the fulcrum as well as in input & output force
1. first-class lever – fulcrum located between the 2 forces, output force is always in the opposite of the input force
2. second-class lever – output force is in between input force & fulcrum (Fout > Fin)
3. third-class lever – input force is in between the output force & fulcrum (Fout < Fin)

11. Levers

12. 2. Pulleys
a. a grooved wheel with a rope, chain, or cable running along the grove.
b. There are 3 types of pulleys:
1. fixed pulleys – wheel doesn’t move, simply changes direction of force
2. movable pulley – one end of the rope is fixed & the wheel is free to move; multiplies force applied
3. block & tackle – system of pulleys that are both fixed & movable; decrease force needed by increasing pulleys

13. Pulleys

14. 3. Wheel & Axle
a. a shaft or axle attached to the center of a large wheel so that they both rotate together.
Ex. doorknob, screw driver, gears
b. you can increase the work of a wheel an axle by increasing the radius of the wheel

15. 4. Inclined Planes
a. is a sloping surface, such as a ramp, that reduces the amount of force required to do work.
Ex. Moving boxes

16. 5. Screw
a. an inclined plane wrapped in a spiral around a cylindrical post. This allows for the forces to be done by all the threads along the screw.

17. 6. Wedge
a. is an inclined plane with one or two sloping edges and changes the direction of the input force

18. II. Compound Machines
A. Compound machines are 2 or more simple machines that operate together.
Ex. Can opener (lever, wedge, wheel & axle)

19. FCAT Science Review: Body Systems
Skeletal System
Muscular System
Nervous System

20. Skeletal System The adult human body is made up of 206 bones.
Infants, however, are born with over 300 bones!
Besides bones, cartilage, ligaments, and other tissues also make up this system

21. Skeletal System Functions: Protects internal organs
Stores and releases fats
Produces blood cells
Stores and releases minerals
Facilities movement
Supports the body

22. Muscular System There are about 700 muscles in the human body
Three types of muscles:
Skeletal muscle: voluntary muscles that help bones move
Smooth muscle: involuntary muscles that carry out processes in internal organs
Cardiac muscle: involuntary muscle that allows your heart to pump blood

23. Muscular System Functions Movement Stabilizes joints Maintains posture
Generates heat during activity

24. Nervous System The nervous system is made up of two parts
Central nervous system
Brain & spinal cord
Peripheral nervous system
All other nerves in the body
Messages are sent through neurons:

25. Nervous System Functions:
Collects sensory input from body & environment
Processes and interprets sensory input
Responds to sensory input