This document discusses simple machines including their definitions, examples, and calculations of mechanical advantage and efficiency. It defines a machine as a device that changes the magnitude or direction of a force. Simple machines include levers, pulleys, inclined planes, screws, and wedges. Complex machines combine two or more simple machines. Ideal mechanical advantage is the ratio of output force to input force. Real machines have efficiencies less than 100% due to friction and other losses. Compound machines link two or more simple machines together such as the combination of a pedal, gear, chain, and wheel that makes up part of a bicycle.

1. SIMPLE MACHINES
SECTION 10.2

2. SIMPLE MACHINES
• How do I define a simple machine?
• How do I differentiate between an ideal and a real
machine?
• How do I define and calculate efficiency?

3. MACHINES
• Machine: a device that changes the magnitude or
direction of a force
• Should make things easier
• Simple machines: bottle openers, screwdrivers, …
• Complex machines: bikes, cars, …

4. BOTTLE OPENER
• How does a bottle opener
work?
• A person applies a force up
• This is called the effort force, Fe
• The opener applies a force to
the cap
• This is called the resistance
force, Fr

5. BOTTLE OPENER
•

6. SINGLE PULLEY
• Fe = Fr
• MA is 1
• Why have a single
pulley?

7. DOUBLE PULLEY
• If we add a pulley,
MA goes over 1
• What happens to
direction?

8. WORK
• Work is Fd
• There is input work and output work
• A machine can increase force but not energy so, …
• Wo = Wi
• Frdr = Fede

9. IDEAL MECHANICAL ADVANTAGE
•

10. MACHINES
• Maximum efficiency is 100%
• Rare
• Most machines are made up of a combination of
• Levers
• Pulleys
• Wheel and axle
• Incline plane
• Wedge
• screw

11. BASIC MACHINES

12. STEERING WHEEL
•

13. COMPOUND MACHINES
• Compound
machine: A
machine with two
or more simple
machines linked
such that the
resistance force of
one machine
becomes the effort
force of the second
machine

14. COMPOUND MACHINES
• The pedal and front gear
are wheel and axel
• Effort force is rider on the
pedal
• Turns into resistance force
of front gear on chain
• This force turns into the
effort force of the chain
• That turns into the
resistance force of the
wheel on the road

15. BICYCLE
•

16. EXAMPLE
• The rear wheel on a bicycle is
35.6 cm and a gear with a
radius of 4.00 cm. When the
chain is pulled with a force of
155 N, the wheel rim moves
14.0 cm. The efficiency of this
part of the bike is 95.0 %. Find
a. IMA of the wheel and gear
(for wheel and axis we can
use the ratio of the radii)
b. MA of the wheel and gear
c. Resistance force
d. How far was the chain
pulled to move the rim 14.0
cm?

17. HOMEWORK
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