What is the definition of "kinetic friction"?
Friction between objects in motion. Kinetic friction is generally less than static friction.

## 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: Mechanical Power Variables 200 Description: This class discusses the variables involved in mechanical power transmission and how they affect industrial processes. Includes an Interactive Lab. Difficulty: Intermediate Number of Lessons: 14 Language: English, Spanish

Class Outline
• Objectives
• What Are Mechanical Power Variables?
• Speed and RPM
• Power
• Horsepower
• Torque
• Torque and RPM
• Gear Ratios
• Thrust
• Friction
• Friction and Heat
• Tension
• Efficiency
• Summary

Class Objectives
• Describe how machine specifications are used.
• Distinguish between the variables used to measure linear speed and rotational speed.
• Calculate a basic power value.
• Define horsepower.
• Define torque.
• Describe the relationships between rpm, horsepower, and torque.
• Describe the relationships between gear ratios, speed, and torque.
• Define thrust.
• Identify types of friction.
• Describe the effects of friction on various machine components.
• Describe the effects of tension in belt and chain drive systems.
• Describe factors that influence efficiency.

Class Vocabulary

Vocabulary TermDefinition
Microscopic peaks found on all surfaces. Contact between asperities causes friction.
An imaginary straight line passing through the center of an object. A round component such as a gear typically rotates around its axis. An axis also indicates the direction of a component's linear motion on a machine tool.
A long, threaded device with reciprocating ball bearings that rotates to move components in a linear direction.
A system consisting of a belt and at least two fixed pulleys that transmit motion from one pulley to the other.
In the metric or SI system, the number of centimeters that a component travels in one minute (cpm).
A system consisting of a chain and sprockets that transmits motion from one sprocket to the other.
The gear that receives energy from a power source, such as an electric motor. Drive gears transmit power to an intersecting driven gear to perform work.
The gear that receives motion from the drive gear on a machine. Driven gears often turn tools or components.
A device used to measure an engine's horsepower or torque.
A measure of the work output of a system versus the total work supplied to it.
A standard system of measurements based on the inch, pound, and Fahrenheit degrees. English measurements are primarily used in the United States and England.
In the English system, the unit used to measure power, abbreviated as ft-lb.
The push or pull that gives energy to an object. A force changes an object's motion or state of rest.
The resistance to relative motion between surfaces. Friction is caused by contact between surface asperities.
The relationship between the number of teeth on two meshing gears used to transmit motion. The gear ratio reflects the change in mechanical advantage resulting from the gears.
A unit of power used to describe machine strength, abbreviated as hp. One horsepower equals 33,000 ft-lbs of work per minute, or 746 watts.
In the English system, the number of linear inches that a component travels in one minute (ipm).
The tendency of an object to remain at rest until acted on by a force.
Friction between objects in motion. Kinetic friction is generally less than static friction.
Motion that takes place along a straight line. Mechanical energy can take the form of rotary or linear motion.
The opposition to applied force, such as a weight to be carried or moved.
A substance used to reduce friction between two surfaces.
The amount of matter that is contained within an object.
Power that is transmitted through a mechanical system and used to perform work.
A standard international system of measurement based on the gram, liter, and meter. Also known as the SI system.
In the metric system, the unit used to measure power and torque, abbreviated as N-m.
The maximum horsepower a machine can exert, achieved at a certain rpm. After horsepower peaks, it will decrease with increasing rpm.
The maximum torque a machine can exert, achieved at a certain rpm. After torque peaks, it will decrease with increasing rpm.
In the English system, the units used to measure torque, abbreviated as lb.-ft.
The rate at which work is accomplished. Power is expressed in ft-lbs. and is the result of the amount of work accomplished divided by the time it took to do the work.
A circular device that is used as a pair in belt drive systems to transmit motion.
The main upper portion of a stamping press that slides up and down within the press frame during operation.
A unit of measurement that indicates the number of revolutions a machine component makes in one minute (rpm).
An abbreviation for the metric system. Since it is used worldwide, SI is the abbreviation for Systeme International, or International System in English.
A description of the essential physical and technical properties of a machine. Specifications or "specs" often include torque and horsepower ratings.
The amount of distance an object travels in a given period of time. Speed is used to measure both linear and rotational movement.
A gear or wheel with metal teeth that meshes with the links of a chain. Sprockets are used in chain drive systems to transmit motion.
Friction between two objects in contact that are not moving. Static friction is generally greater than kinetic friction and must be overcome before an object can be set in motion.
A pulling force that is directed away from the object and attempts to stretch or elongate the object. Tension affects belt and chain drive systems.
A force that occurs when an object is accelerated in one linear direction. Thrust can be expressed by the equation force = mass x acceleration.
A force that produces rotation. Torque is measured in pound-feet in the English system and Newton-meters in the metric system.
A unit used to measure power. 746 watts equal one horsepower.
The gradual removal of material on a surface caused by contact between surface asperities.
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.
A cylindrical, screw-shaped shaft that is used with a worm gear to transmit motion.
A gear drive consisting of a long, cylindrical device with a spiraling groove that intersects with the teeth of a wheel-like gear. A worm gear drive is used to transmit motion between nonintersecting perpendicular shafts, and the cylindrical "worm" is always the drive gear.