February 23, 2025

• Do Now: Read through the Lever Lab directions and answer the first three questions

• Find the weight in Newtons of the gravel container by using the spring scale (that is your resistance)

• Homework: Study for test and finish contract project

First Class

Second Class

Third Class

Today

• Lever Lab• Review last test• Review Incline Plane results• Kahoot

Six Simple Machines

• Inclined Plane• Wedge• Screw

• Lever• Pulley• Wheel & Axle

Mechanical Advantage

Terminology

Where your hands are• Effort• Input• Output DISTANCE

Where the load is• Load• Output• Resistance• Input DISTANCE

Mechanical Advantage

Effort Force = Output Distance = Resistance Distance = Input Force

Resistance Force = Input Distance = Effort Distance = Output Force

Other forms of the MA formula:

Mechanical Efficiency

Mechanical Efficiency = Work Output X 100 Work Input

Inclined Plane

• Reduces force, but increases distance• The mechanical advantage of an inclined plane

is length divided by height. • Wedges and screws are types of inclined

planes.

MA = L/H

Wedge

• A wedge generates outward forces• A wedge is a type of inclined plane. Its

mechanical advantage is its length divided by its greatest thickness.

Screw

• A screw is an inclined plane wrapped around a cylinder

• Uses a small force over a longer distance

• The closer the threads, the lower the force required

Levers – Three Classes

• Can change direction & size of force• In a first-class lever, the fulcrum is between

the force and the load.• In a second-class lever, the load is between

the force and the fulcrum. • In a third-class lever, the force is between the

fulcrum and the load.

First Class LeverChange direction & maybe force

Second Class LeverChange force, but not direction

Third Class LeverDon’t change direction, output < input

Pulleys

• Change direction and may change input force• Types of pulleys include fixed pulleys, movable

pulleys, and block and tackles.

Wheel and Axle

• The mechanical advantage of a wheel and axle is the radius of the wheel divided by the radius of the axle.

Compound Machines

• Compound machines consist of two or more simple machines.

• Compound machines have low mechanical efficiencies because they have more moving parts and therefore more friction to overcome.