Simple Machines-a machine that does work with one movement

Levers A bar that is free to pivot, or turn,

about a fixed point Fulcrum- fixed point on the lever Input arm- part of lever that person

adds input force to Output arm- part of lever that moves

the output force or work

3 types of Levers

First class lever Fulcrum is located between the input force and

the output force screwdriver opening paint can HW: 5 1st class levers

Second class lever Ouput force is located between the

input force and the fulcrum Wheel barrow

fulcrum

Input force

Output force

Third class lever Input force is located between the

output force and the fulcrum Baseball bat, rake, hockey stick

fulcrum

Input arm

Output arm

Mechanical advantage of lever

MA = length of input arm = Li

length of output arm Lo

Homework Calculate the MA of a wheel barrow

that has 5 feet from the wheel to handle. The center of the load is exactly 2.5 feet from the wheel.

What would you do to design a better wheel barrow?

Pulleys Grooved wheel with a rope, chain,

or cable running through the groove

Fixed pulleys Change direction of force Gravity Help! MA = 1

Move when a force is applied. MA = 2 Multiply the input force 2x.

Movable Pulleys

Pulley SystemsBlock and Tackle

A system of fixed and movable pulleys

MA = number of ropes supporting the weight

Do not count rope that you pull down on.

Do count a rope that you pull up on.

Wheel and Axle Two wheels of different sizes that

rotate together Can you think of any?

Doorknobs Faucets Steering wheel Stereo volume knobs

Gears Form of wheel and axle Two wheels of different sizes with

interlocking teeth Multiply the input force, input

distance, and change direction of force

Mechanical advantage of W&A

MA = radius of wheel rw

radius of axle ra

Inclined Planes A sloping surface that reduces the

amount of force needed to do work Ramps Roads

Mechanical advantage of IP MA = length of slope l height of slope h

h

l

Screw Inclined plane wrapped around a

cylindrical post Wood screws Soda lids Olive jars

Wedge Inclined plane with one or two

sloping sides that moves through an object or material to change the direction of the force. Knives Axes

Compound Machines Two or more simple machines

working together to perform a task Scissors Faucets Jeeps

The End

Calculations are next!

Calculations Calculate the Mechanical

Advantage of a lever that has an input arm of 15 meters and a output arm of 3 meters.

15 m

3 m

fulcrum

MA of levers MA = length of input arm length of output arm

= 15 m 3 m

= 5

MA of a Wheel and axle Calculate the MA of the door knob

that you turn as you try to sneak into Mr. Miller’s room tardy.

The knob itself has a radius of 12 cm and the axle that runs through the knob as a radius of 1.2 cm.

MA of W&A = radius of wheel radius of axle

= 12 cm 1.2 cm

= 10

MA of an Inclined Plane Calculate the mechanical

advantage of an inclined plane/ramp used to load your ATV onto the bed of a truck.

The truck’s bed is exactly 2 meters off the ground and the ramp is 8 meters long.

MA of I.P. = length of ramp height of ramp

MA = 8 m 2 m = 4

2 m

8 m

MA of pulleys!

120 N

120 N

120 N

120 N