What is the definition of "first-class lever"?
A lever in which the fulcrum is positioned between the load and the effort. A crowbar is an example of a first-class lever.

Learn more about first-class lever in the class Intro to Mechanical Systems 100 below.


Mechanical Systems Training


Class Information
Tooling U-SME classes are offered at the beginner, intermediate, and advanced levels. The typical class consists of 12 to 25 lessons and will take approximately one hour to complete.
Class Name:Intro to Mechanical Systems 100
Description:This class examines simple machines such as the lever and inclined plane and covers basic concepts of physical science, including mechanical advantage and friction.
Prerequisites: none
Difficulty:Beginner
Number of Lessons:20
Language:English, Spanish
 
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Class Outline
  • Objectives
  • Mechanical Systems
  • Mechanical Advantage
  • Mechanical Advantage and Distance
  • Friction
  • The Lever
  • Classes of Levers
  • The Wheel: Moveable Pulleys
  • Arrangements for Moveable Pulleys
  • The Moveable Pulley: Mechanical Advantage
  • The Wheel and Axle
  • The Fixed Pulley
  • The Gear
  • Types of Gears
  • The Cam
  • The Inclined Plane
  • The Wedge
  • The Screw
  • Mechanical Components
  • Summary
  
Class Objectives
  • Define machine.
  • Describe mechanical advantage.
  • Describe the relationship between distance and mechanical advantage.
  • Define friction.
  • Describe the lever.
  • Identify the classes of levers.
  • Describe the moveable pulley.
  • Describe common arrangements for moveable pulleys.
  • Describe the mechanical advantage of moveable pulleys.
  • Describe the wheel and axle.
  • Describe the fixed pulley.
  • Describe the gear.
  • Identify types of gears.
  • Describe the cam.
  • Describe the inclined plane.
  • Describe the wedge.
  • Describe the screw.
  • Identify common secondary mechanical components.

Class Vocabulary

Vocabulary TermDefinition
angular gear train A type of gear with slanted teeth that is designed to allow power transmission between gears of intersecting shafts. Some examples of angular gear trains are bevel gears and miter gears.
applied force The energy or effort provided to a machine to perform work. Applied force has many forms, from the power of an electric motor to the push from human hands.
axis The center around which a wheel or component rotates.
axle The center post of a wheel. The axle is positioned on the wheel's axis.
bearing A rotating support placed between components to increase movement and reduce friction. Ball bearings are a common type of this device.
belt An endless loop of material used to transmit motion between two or more pulleys. Belts require friction to stay in contact with the pulleys.
bevel gear A type of gear with cone-shaped teeth that are cut at an angle. Bevel gears are often used in angular gear trains.
block and tackle The common name for a moveable pulley.
brake A device used to stop motion.
breech The side opening on a moveable pulley that provides access to the sheave.
cam A low-friction, circular lever consisting of a lobe and a shaft that transforms circular motion into linear motion. Cams are often used in combustion engines.
clutches Devices used to engage or disengage rotating parts.
delivered force The result of the effort applied to a machine, such as a weight rising in the air or a wheel turning. Delivered force is the resulting movement or work performed by a machine.
distance The space between two points or objects. Distance is the amount of space through which the supplied and delivered forces travel, which is a requirement for mechanical advantage.
doorstop A wedge used to hold open a door by placing it between the bottom of the door and the floor.
drive gear The gear that is attached to the power source, such as an electric motor. Drive gears transmit power to driven gears to perform work.
driven gear The gear that receives motion from the drive gear on a machine. Driven gears often turn tools or components.
driven pulley The pulley on a machine that receives power from the driver pulley via a belt.
driver pulley The pulley on a machine that is attached to the power source, such as an electric motor.
effort The force applied to an object or machine to cause motion.
first-class lever A lever in which the fulcrum is positioned between the load and the effort. A crowbar is an example of a first-class lever.
fixed block A type of moveable pulley that is fixed to a point overhead. One end of the rope is then attached to the load, while the free end is pulled to raise the load.
fixed pulley A device consisting of a wheel rigidly fixed to a shaft that is used with a belt to transmit energy and motion to another fixed pulley.
follower A device that works with a cam to transform circular motion into linear motion. The follower, which is attached to a shaft, stays in contact with the lobe and moves the shaft up and down as the lobe rotates.
four-bar linkage A multi-lever device used to convert rotary motion into reciprocating motion.
friction A force that resists motion between two objects that are in contact with each other. Smoother surfaces exhibit less friction, while rougher surfaces exhibit more friction.
friction-based machine A machine that requires some amount of friction to function. Friction-based machines, such as screws, require friction to keep from slipping or moving.
fulcrum A pivot point of a lever, or the point around which an object turns.
gear A disc or wheel that contains evenly spaced teeth around its perimeter. Gears are usually used in pairs to transmit energy and motion.
helical gear A type of gear with slanted teeth. Helical gears are quieter than spur gears.
herringbone gear A type of gear that has angled teeth in the shape of a letter "V." Herringbone gears resist side loading.
inclined plane A simple machine consisting of a flat, angled surface used to raise objects. The mechanical advantage of an inclined plane increases with its length.
jack A device that consists of a large screw used to raise a heavy object, such as a car or building.
lever A type of simple machine consisting of a rigid bar that pivots on a fulcrum. Levers are used to transmit motion and alter mechanical advantage.
linear motion Motion that takes place in a straight line rather than in a circle around an axis.
load The opposition to applied force, such as a weight to be carried or moved.
lobe The portion of a cam that intersects with the follower to transmit motion. Lobes are commonly shaped like an oval.
low-friction machine A machine that functions best when minimal friction is present. Low-friction machines, such as levers, maximize mechanical advantage.
lubrication The use of a slippery substance, such as oil or graphite, placed between two moving surfaces that are in contact with each other. Lubrication minimizes friction, which aids movement and reduces heat.
machine A device whose primary purpose is to transform energy into motion to accomplish some form of useful work.
mechanical advantage The difference between the applied force and the work accomplished. Mechanical advantage allows machines to perform more work with less effort.
mechanical system A collection of machines functioning together to perform useful work.
miter gear A type of bevel gear used in pairs with intersecting shafts at 90° angles. Both the driving gear and driven gear in a miter gear pair have the same diameter, same number of teeth, and a mechanical advantage of 1.
moveable pulley A device consisting of a shell, a moveable wheel, and a rope that is used to raise a load. Moveable pulleys, also known as block and tackle, may be attached overhead or to the load itself.
nut A fastening device containing a hole and internal threads that mate with a screw or bolt.
perpendicular An intersection of two lines or objects at right angles. The delivered forces exerted by a wedge are perpendicular to its direction of travel.
physical science The study of non-living matter. Physical science includes physics, chemistry, astronomy, and geology.
pulley A circular device that is used to raise or lower a load or transmit motion. A pulley may be moveable or fixed.
rack and pinion A type of gear that consists of a rack, which is a bar containing teeth, and a pinion, which is a round gear. Rack and pinion devices are commonly used on automotive steering mechanisms.
ramp A type of inclined plane. A ramp is often used to load materials onto a truck bed or to allow pedestrians to walk from one level to another.
reciprocating Alternating or back and forth.
resistance The opposition to a force, such as the weight of a load or friction to movement.
runner A type of moveable pulley that is attached to the load. One end of the rope is fixed to a point overhead, while the other is pulled to raise the load.
screw A type of inclined plane set around a cylinder. Screws are often used to fasten materials or transmit motion.
second-class lever A lever in which the load lies between the fulcrum and the effort. A wheelbarrow is an example of a second-class lever.
see saw A long, narrow board equally balanced in the middle on a fulcrum.
shaft A long cylindrical device such as a rod or pole. On a wheel, the shaft extends from the center of the wheel along its axis.
sheave The freely moving wheel that is part of a moveable pulley. The sheave usually contains a groove to hold a rope or chain.
shell The outer covering on a moveable pulley.
shim A thin wooden wedge used in woodworking to tighten and fill gaps in loose wooden parts.
side load A force that occurs when gears are meshed together at an angle, which can lead to deflection and wear.
speed The rate at which an object travels. Speed describes the rate at which supplied and delivered forces move.
spring A flexible device used to apply force, control motion and vibration, and store energy.
spur gear A type of gear that has straight, flat-topped teeth set parallel to the shaft. Spur gears are good for transferring motion.
third-class lever A lever in which the effort is placed between the fulcrum and the load. A baseball bat is an example of a third-class lever.
thread The wedge-shaped circular feature on a screw that serves as the inclined plane.
valve stem A moveable shaft commonly used with a follower and cam to open and close holes in a device such as an engine.
wedge A friction-based inclined plane used to spread apart two opposing forces. A wedge is often used to split wooden logs.
wheel A circular machine that turns on a center axis. A wheel is a circular lever.
wheel and axle A wheel that is rigidly fixed to a central post that rotates with the wheel. A fixed pulley is an example of a wheel and axle.
work The result of a force applied to an object and the distance through which the force is applied. In an equation, work is force multiplied by distance.