Forces of Machines 121

acceleration

An increase in the rate of an object's velocity. Acceleration occurs when a force changes an object's momentum.

angle

A figure formed by the intersection of two lines. Angles are also used to measure distances around a circle.

angular displacement

The change in an object's angular position. Angular displacement is the difference between an object's final position on a circle and its starting position on the circle.

angular frequency

A measure of circular motion. Angular frequency, or rotary speed, is equal to the number of revolutions an object makes divided by the amount of time passed.

angular motion

Movement that takes place along a circle's circumference. Angular motion, which is also called rotary motion or circular motion, is one of two basic forms of motion that mechanical energy can take.

angular velocity

The angular change of position in a specific amount of time. Angular velocity, which is also called rotary velocity, is measured in either degrees per second or radians per second.

area

The size of the space contained within an enclosed two-dimensional figure. Area is typically measured in square units such as square inches or square centimeters.

asperities

Microscopic peaks found on all surfaces. Contact between asperities on different surfaces causes friction.

attraction

A type of force that draws objects with opposite electrical charges toward each other. Attraction results from both electromagnetism and gravity.

axis

An imaginary straight line that passes through the center of an object. Objects typically rotate around an axis.

bearing

A friction-reducing device that allows one moving part to glide past another moving part. Bearings operate using a sliding or rolling mechanism.

belt

A band of flexible material that is looped around two or more fixed pulleys to transmit motion. Belts are made of various materials and come in different types, such as flat belts, round belts, and V-belts.

belt drive system

A mechanical system consisting of a flexible belt and at least two round, fixed pulleys. Belt drive systems are used to transfer motion between machine components.

cam

A low-friction, circular lever consisting of multiple lobes and a shaft that transforms circular motion into linear motion. Cams are often used in combustion engines.

circular motion

Movement that takes place along a circle's circumference. Circular motion, which is also called rotary motion or angular motion, is one of two basic forms of motion that mechanical energy can take.

circumference

The boundary or outside edge of a circle. Circumference measures the distance around a circle.

clockwise

Circular motion that resembles the motion of clock hands. Clockwise rotation proceeds to the right from the top of a circle.

coefficient of friction

The relationship between the force required to move an object along a surface to the force that presses those two surfaces together. Objects with a greater coefficient of friction require greater force to produce motion.

contact force

An interaction that causes a change in an object's motion or state of rest by physically touching the object. Contact forces include friction and torque.

counterclockwise

Circular motion that resembles the reverse motion of clock hands. Counterclockwise rotation proceeds to the left from the top of a circle.

deceleration

A reduction in the rate of an object's velocity. Deceleration occurs when a force changes an object's momentum.

degrees

A unit of measurement used in the English system for angles and circular motion. There are 360 degrees in a complete circle.

degrees per second

A unit of measurement used in the English system for rotary, or angular, velocity. Degrees per second measures the change in the angular position of an object, in degrees, every second.

direction

The path in which a force causes an object to move. Direction is often affected by outside forces, especially gravity.

displacement

An object's overall change in position. Displacement is the difference between an object's final position and its starting position.

distance

The space between two points or objects. Distance is the amount of space through which supplied and delivered forces travel.

dynamic force

A force that causes a change in velocity. Dynamic forces are not in a state of equilibrium.

dynamics

A subdivision within the science of mechanics. Dynamics studies the forces that cause and/or affect an object's rate of motion.

electromagnetism

A force of attraction between certain types of metals or objects charged with static electricity. Electromagnetism is produced by an electric current.

energy

The ability to do work. Energy, which is never created or destroyed, may be potential or kinetic and may appear as electrical, mechanical, thermal, or chemical energy.

English system

A standard system of measurements based on the inch, second, pound, and Fahrenheit degrees. English measurements are primarily used in the United States and England.

equilibrium

A state of balance or sameness. Objects that are in equilibrium are either completely still or moving at a consistent rate.

feet per minute

fpm. An English-system unit that usually indicates machine speed, or how many feet a machine component travels in one minute. Feet per minute equals the distance traveled in feet divided by the time spent traveling.

First Law of Motion

A scientific rule stating that an object will remain at rest or in its original motion until acted upon by an unbalanced force. The First Law of Motion, or the Law of Inertia, is one of three scientific laws that Sir Isaac Newton developed to describe the behavior of moving objects.

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.

foot

ft. A unit of linear measurement in the English system that equals 12 inches. One foot equals 30.48 centimeters or 0.30 meters in the metric system

force

An influence, such as a push or a pull, which produces a change in an object's motion or state of rest. Forces have specific directions and magnitudes.

forklift

A type of powered industrial truck (PIT) that has two prongs on the front for lifting pallets of material. Forklifts are one of the most common types of PIT.

friction

A force that resists motion between two objects that are in contact with each other. Friction is a type of contact force used in mechanical systems.

gear

A round or cylindrical mechanical component with teeth that is used to transmit power. Gears are designed to mesh with one another in order to alter the speed, torque, or direction of mechanical energy.

gravity

The force of attraction between masses. Gravity is the force that makes objects fall to the ground.

inch

in. A small unit of linear measurement in the English system. One inch equals approximately 2.54 centimeters in the metric system.

inches per minute

ipm. An English-system unit that usually indicates machine speed, or how many inches a machine component travels in one minute. Inches per minute equals the distance traveled in inches divided by the time spent traveling.

inertia

The tendency that objects have to resist changes to their state of motion. Inertia causes an object to either remain at rest or in its original state of motion until it is acted upon by an outside force.

kilometer

km. A unit of linear measurement in the metric system that is usually used to measure long distances. One kilometer equals 1,000 meters, or 0.62 miles in the English system.

kilometers per hour

kph. A metric-system unit that indicates speed, or how many kilometers an object travels in one hour. Kilometers per hour equals the distance traveled divided by the time spent traveling.

kinetic energy

Energy existing due to an object's motion. Kinetic energy is released when a spring deflects and returns to its original shape.

kinetic friction

Friction between objects in motion. Kinetic friction, which is also called sliding friction, is generally lower than static friction.

Law of Inertia

A scientific rule stating that an object will remain at rest or in its original motion until acted upon by an unbalanced force. The Law of Inertia, or the First Law of Motion, is one of three scientific laws that Sir Isaac Newton developed to describe the behavior of moving objects.

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

Movement along a straight line. Linear motion, which is also called rectilinear motion, is one of two basic forms of motion that mechanical energy can take.

linear speed

The rate at which an object travels along a straight path. Linear speed describes the amount of distance an object travels in a given period of time.

linear velocity

The rate at which an object traveling along a straight path changes its position during a given amount of time. Linear velocity is equal to the object's total displacement divided by time.

lobe

The portion of a cam that intersects with the follower to transmit motion. Lobes have a variety of shapes but are most commonly shaped like an oval.

machines

A device consisting of two or more parts that transform energy into motion. Machines are used to transmit or modify force and motion so as to accomplish some form of useful work.

magnet

A metallic object or substance that possesses a force that attracts or repels other metals. Magnets attract opposite charges and repel like charges.

magnitude

A measurement of the size, amount, or quantity of force. The magnitude of a force affects the way in which the force changes an object's motion.

mass

The amount of matter in an object. Mass gives an object weight when it is acted upon by gravity.

matter

The material or substance that makes up an object. Matter has both mass and volume.

mechanical system

A collection of machines functioning together to perform useful work. All modern mechanical systems are based on simple machines.

mechanics

The branch of physics concerned with the motion of objects. Mechanics deals with different forces that cause or prevent motion.

meter

m. A base unit of linear measurement in the metric system. One meter equals 3.28 feet in the English system.

meters per minute

m/min. A metric-system unit that usually indicates machine speed, or how many meters a machine component travels in one minute. Meters per minute equals the distance traveled in meters divided by the time spent traveling.

metric system

A standard system of measurements based on the meter, second, kilogram, and Celsius degrees. The metric system is internationally recognized.

mile

A unit of linear measurement in the English system that equals 5,280 feet and is used to measure long distances. A mile equals 1,609.34 meters or 1.61 kilometers in the metric system.

miles per hour

mph. An English-system unit that indicates speed, or how many miles an object travels in one hour. Miles per hour equals the distance traveled divided by the time spent traveling.

millimeter

mm. A small unit of linear measurement in the metric system. One millimeter equals approximately 1/1000 meter, or 0.039 of an inch in the English system.

millimeters per minute

mm/min. A metric-system unit that usually indicates machine speed, or how many millimeters a machine component travels in one minute. Millimeters per minute equals the distance traveled in meters divided by the time spent traveling.

momentum

The product of the mass and velocity of an object in motion. The momentum of a moving object changes when a force acts upon the object.

motion

A change in an object's original position as a result of a force applied to the object. Motion is typically described in terms of displacement, direction, velocity, acceleration, and time.

Newton’s Laws of Motion

A set of three scientific rules that describe the behavior of moving objects. Sir Isaac Newton established the Laws of Motion in the late 1600s.

non-contact force

An interaction that causes a change in an object's motion or state of rest without physically touching the object. Non-contact forces include gravity and electromagnetism.

perpendicular

An intersection of two lines or objects at right angles. A vertical line is perpendicular to a horizontal line.

point of application

The place on an object where a force is applied. Point of application can affect forces such as torque and momentum.

potential energy

Stored energy with the potential to do work. Machines that have large components that raise and lower, such as a press, contain potential energy that becomes kinetic energy when it is released.

pulley

A type of simple machine consisting of a circular device that raises or lowers a load or transmits motion. Pulleys may be moveable or fixed.

radians

rad. A unit of angular measurement for the metric system. One radian is equal to approximately 57.30 degrees.

radians per second

A unit of measurement used in the metric system for rotary, or angular, velocity. Radians per second measures the change in the angular position of an object, in radians, every second.

rectilinear motion

Movement along a straight line. Rectilinear motion, which is also called linear motion, is one of two basic forms of motion that mechanical energy can take.

revolutions per minute

rpm. The number of times an object rotates 360 degrees, or in a complete circle, in one minute. Revolutions per minute is a measurement of speed.

rotary motion

Movement that takes place along a circle's circumference. Rotary motion, which is also called circular motion or angular motion, is one of two basic forms of motion that mechanical energy can take.

rotary motion

Movement that takes place along a circle. Rotary motion, which is also called circular motion or angular motion, is one of two basic forms of motion that mechanical energy can take.

rotary speed

A measure of circular motion. Rotary speed, or angular frequency, is equal to the number of revolutions an object makes divided by the amount of time passed.

rotary velocity

The angular change of position in a specific amount of time. Rotary velocity, which is also called angular velocity, is measured in either degrees per second or radians per second.

rotational axis

An imaginary straight line at the center of rotating objects. The rotational axis passes through all of an object's fixed, or stationary, points, while all of the object's other points rotate around the line.

scalar quantity

An amount or measurement that is not related to direction. Scalar quantities include speed, volume, and temperature.

Second Law of Motion

A scientific rule stating that the rate at which an object will move, or accelerate, depends on the amount of force applied to the object and the mass of the object itself. The Second Law of Motion is one of three scientific laws that Sir Isaac Newton developed to describe the behavior of moving objects.

simple machines

A basic mechanical device that uses mechanical advantage to multiply, transform, or change the direction of force. Simple machines include the lever, wheel, and inclined plane.

Sir Isaac Newton

A 17th century English physicist and mathematician who discovered the laws of gravity and motion. Sir Isaac Newton's scientific discoveries established almost all of the foundation for classical mechanics and modern physics.

sliding friction

Friction between objects in motion. Sliding friction, which is also called kinetic friction, is generally lower than static friction.

speed

The amount of time it takes for an object to travel a given distance. Speed is used to measure both linear and rotational movement.

spring

An elastic device used to dampen and apply force, control motion and vibration, and store energy. Springs are used in many mechanical systems to aid in the storage and transfer of energy.

static electricity

An electrical charge that builds up due to friction between two dissimilar materials. When discharged, static electricity can cause a slight shock.

static force

A force that maintains a constant velocity. Static forces are in a state of equilibrium.

static friction

Friction between two objects that are in contact but not moving. Static friction is generally greater than kinetic friction and must be overcome before an object can be set in motion.

statics

A subdivision within the science of mechanics. Statics studies the forces that keep objects in a state of equilibrium.

temperature

A measurement of the degree of heat within an object. Temperature is a scalar quantity because it is not related to or dependent upon direction.

Third Law of Motion

A scientific rule stating that every action or force produces an equal and opposite reaction. The Third Law of Motion is one of three scientific laws that Sir Isaac Newton developed to describe the behavior of moving objects.

three-dimensional

3D. Having a length, depth, and width. Three-dimensional objects possess mass and volume.

torque

A force that produces rotation. Torque is measured in pound-feet in the English system and Newton-meters in the metric system.

variables

A value, factor, or element that is liable to change. Variables do not remain the same over a period of time and/or space.

vector quantity

An amount or measurement that is related to a direction. Vector quantities include velocity, acceleration, and weight.

velocity

The rate at which an object changes position during a given amount of time. Velocity, unlike speed, is a vector quantity because it always implies a direction.

volume

The amount of three-dimensional space that an object occupies. Volume is a scalar quantity because it is not related to or dependent upon direction.

weight

A measurement of the gravitational pull on an object on the earth's surface. Weight is expressed in the English system using the pound or the ounce and in the metric system using milligrams, grams, and kilograms.

work

The result of a force applied to an object and the distance through which the force is applied. Work is force multiplied by distance.

wrench

A type of manual assembly tool that tightens and turns bolts and nuts. Wrenches contain fixed or moving jaws or a round attachment that grips the nuts or bolts.