1. Unit 2 Force & Motion
Ch. 8 Sec. 3
Simple Machines

2. Types of Machines simple machine - does work w/ only 1 movement
ex. inclined plane, wedge, screw, lever, wheel and axle, pulley
compound machine - made up of a combination of simple machines
ex. can opener & bike

3. Inclined Plane
inclined plane - slanted surface used to change an object’s elevation
ex. ramp
makes work easier by…
increasing the distance a force is applied
increase in length = greater mechanical advantage
Mechanical Advantage
𝑴𝑨= 𝒍 𝒉

4. Wedge wedge - made up of 2 inclined planes and moves
ex. knife, axe, front teeth
makes work easier by…
changing the direction of a force
increase in length and thinness = greater mechanical advantage
Mechanical Advantage
𝑴𝑨= 𝒍𝒆𝒏𝒈𝒕𝒉 𝒘𝒊𝒅𝒕𝒉/𝒕𝒉𝒊𝒄𝒌𝒏𝒆𝒔𝒔

5. Screw screw - an inclined plane wrapped around a cylinder
ex. screw, base of a light bulb, mouth of a jar
makes work easier by…
changing the direction of a force
more threads = greater mechanical advantage

6. Wheel & Axle
4) wheel & axle - consists of 2 circular objects of different sizes (larger = wheel; smaller = axle)
ex. steering wheel, screwdriver, faucet handle, ferris wheel
makes work easier by…
increasing a force
Mechanical Advantage
𝑴𝑨= 𝒘𝒉𝒆𝒆𝒍 𝒓𝒂𝒅𝒊𝒖𝒔 𝒂𝒙𝒍𝒆 𝒓𝒂𝒅𝒊𝒖𝒔

7. Lever
5) lever - rigid bar that moves about a fixed point called the fulcrum
ex. seesaw, scissors, broom, baseball bat
makes work easier by…
increasing distance or force, &/or changing direction of a force

8. 3 Classes of Levers 1st Class Levers
fulcrum is in-between input force and load
ALWAYS changes direction of input force

9. 3 Classes of Levers 2nd Class Levers
load is in-between input force and fulcrum
does NOT change direction of input force
output force > input force

10. 3 Classes of Levers 3rd Class Levers
input force is in-between the fulcrum and load
do NOT change the direction of the input forces
do NOT increase the input force

11. Mechanical Advantage of Levers

12. Pulley pulley - a grooved wheel w/ a rope wrapped around it
ex. flagpole, window blind
makes work easier by…
changing direction of a force or increasing a force

13. Types of Pulleys
Fixed: attached to something that does not move, changes the direction of the force (MA = 1)
Movable: attached to an object being moved, increase force and distance (MA = 2)
Block & Tackles (pulley system): combination of fixed and movable pulley (MA = # of rope segments)