Transcript Unit 2 Force & Motion Ch. 8 Sec. 3 Simple Machines Types of Machines • simple machine - does work w/ only 1 movement – ex.

Unit 2
Force & Motion
Ch. 8 Sec. 3
Simple Machines
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
Inclined Plane
1) 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
𝒍
𝑴𝑨 =
𝒉
Wedge
2) wedge - made up of 2
inclined planes and
moves
– ex. knife, axe, front
teeth
• makes work easier by…
changing the
direction of a force
Mechanical Advantage
𝒍𝒆𝒏𝒈𝒕𝒉
𝑴𝑨 =
𝒘𝒊𝒅𝒕𝒉/𝒕𝒉𝒊𝒄𝒌𝒏𝒆𝒔𝒔
• increase in length and
thinness = greater
mechanical advantage
Screw
3) 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
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
𝒘𝒉𝒆𝒆𝒍 𝒓𝒂𝒅𝒊𝒖𝒔
𝑴𝑨 =
𝒂𝒙𝒍𝒆 𝒓𝒂𝒅𝒊𝒖𝒔
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
3 Classes of Levers
1st Class Levers
• fulcrum is in-between
input force and load
• ALWAYS changes
direction of input force
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
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
Mechanical Advantage of Levers
Pulley
6) 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
Types of Pulleys
1) Fixed: attached to something that does not move, changes
the direction of the force (MA = 1)
2) Movable: attached to an object being moved, increase
force and distance (MA = 2)
3) Block & Tackles (pulley system): combination of fixed and
movable pulley (MA = # of rope segments)