1. Chapter 14 Lesson 4
The Simple Machine

2. I. Lever System
A. Def – A lever is a bar that is free to pivot or turn about a fixed point.
B. Parts of a lever
1. Fulcrum – fixed point of the lever
2. Effort arm – part where force is applied to the lever.
3. Resistance arm – part where the resistance is found on the lever.

4. C. Ideal Mechanical Advantage
1. IMA = Length of effort arm
Length of resistance arm or Le Lr

5. 2. Ex: A worker uses an iron bar to raise a manhole cover weighing 65 N. The effort arm of the lever is 60 cm long. The resistance arm is 10 cm long. What is the ideal mechanical advantage of the bar?
Le =
Lr =
= 6 (IMA)
60 cm
10 cm

6. D. Types of Levers
1. 1st Class
-E – F – R
-Common Ex:
teeter totter
scissors
pliers
claw of hammer

8. 2. 2nd Class
- F – R – E
- Common Ex:
stapler
bottle opener
wheelbarrow
nut cracker

10. 3. 3rd Class (increase speed)
- F – E – R
- Common Ex:
fishing rod
tweezers
mousetrap
baseball bat
softball bat

14. II. Pulleys
A. Def – a grooved wheel with a rope or chain running along the groove.
1. similar to 1st class lever
2. uses rope instead of bar
3. has effort arm and resistance arm.

15. -Fixed – pulley does not move 2. Movable
B. Types of Pulleys
1. Fixed
-Fixed – pulley does not move
-MA = 1
2. Movable
-Movable – pulley is movable
-MA = 2 (can vary)

16. 3. Block and Tackle
-uses fixed and
movable
-Large Mechanical
advantage
-MA = # of ropes in
the pulley system
-MA = 2

17. What is the MA?
= 4

18. III. Wheel and Axle
A. Def – a simple machine consisting of 2 different sized wheels that rotate together.
1. Parts
-small wheel = axle
2. Effort force is applied to large wheel
3. Large wheel turns the axle
4. IMA = rw / ra
5. Ex: Bike, doorknobs, ice cream makers, cars…

20. 6. Ex: An ice cream maker has a wheel radius of 20cm
6. Ex: An ice cream maker has a wheel radius of 20cm. The axle has a radius of 15 cm. What is the ideal mechanical advantage of the wheel and axle?
20 / 15
=1.3 IMA

21. IV. Inclined Plane, Wedge, Screw
A. Inclined Plane
1. Def – a sloped surface used to raise objects
2. IMA = length of slope / height of slope
3. Ex: any ramp
4. Remember** Force is smaller but distance is greater.

23. B. Screw
1. Def – Inclined plane wrapped in a spiral cylindrical post.
2. Ex: screws, lids, drill bits

24. C. Wedge
1. Def – Inclined plane with 1 or 2 sloping sides
2. Used to cut or split
3. Ex: knives, ax blades, chisels…