Mechanical Engineering Study Guide 2025

Machine - --A device that uses energy to do work to accomplish some desired activity -They do not produce energy, but they do transmit and transform energy -Machines can transmit a force, control its motion, and change its direction -A machine is a system of components Component - -A small piece that makes up a larger whole. Each component is there for a specific job, but the sum of components System - -A combination of components Mechanical Engineering - --The designing of machines that contribute to society and our quality of life -Mechanical engineers apply the principles of mathematics, chemistry, and physics to solve real-world problems Dimension - --Describes a physical property of anything -What we are measuring Base Dimensions - --Are independent of other dimensions -They are limited in number -length, mass, time, temperature, force Derived Dimension - --Derived from, or composed of, base dimensions i.e. Area (length x width), Weight (mass x acceleration), velocity (length/time) System International (SI) - -The standard system of units that uses base 10 and used in the rest of the world. -US does not use, but Great Britain does -Base Units: mass-kilograms (kg), length-meters (m), and time-Seconds (S) -Force is a derived unit measured in newtons (N) US Customary - -A system adopted from an old British system of units in the 13th century -Engineering system -Units: length-foot (ft), time-second (s), force-(lbs) -Mass is a derived unit called a slug -Political/Economic choice -Awkward Length - -The magnitude of something in a particular direction Mechanical Mechanical Mass - --The amount of atoms and molecules in something -Matter is energy that has become solid -An object gains mass when it gains more energy and vice a versa -Units: SI-kgs and USA: Slugs, lbs Temperature - -An indication of kinetic energy of mass at the molecular level Area - --A flat, two dimensional property -Units of length multiplied by length describe area -A=length x width Volume - --Three-dimensional property measured in units of length times length times length -V=length x width x height Units for Pressure - --psi -newtons -pascals Metrology - -The branch of science and engineering involving measurement Engineers and scientists need a common language - -Dimensions and units Dimensions are measured by units - -... Units - -Used to measure or quantify -US Common: Absolute and Gravitational -SI: absolute Conversions - --Allows comparison between different measuring systems and units -Necessary to market internationally Effort - --The force simple machines use to do work on a single load or against a single force -When a simple machine increases a force it is at the expense of a decrease in the distance the load is moved -When the work done by the effort just equals the work done by the load, no movement of the machine will occur -When the work done by the effort exceeds the work done by the load, the load will move Mechanical Advantage - --If the force needed to operate the machine (input force) is less than the force being opposed or the load being moved (output force) -The ratio of the output force divided by the input force Mechanical Mechanical -If the number is greater than one, there is a mechanical advantage equal to that number Inclined Plane - --A flat, sloping surface -The only simple machine that does not move -The force is applied to the ramp, since this is the direction the load weight is moved -Sloping side is longer than vertical side -Less force is required to accomplish the same amoung of work with the inclined plane -Trade off more distance for less force -MA=Leverage -WD=FD -MA=W/F or D/d Newton's First Law of Motion - --Every object continues in motion in a straight line unless acted upon by some force -Every object at rest continues at rest unless acted upon by a force -So forces cause a change in an object's state of motion Forces - -Can be applied: -By direct contact: push, pull, twist -At a distance: gravity, magnetism Can change: speed, direction, shape, units of force Newton's Second Law - --Force and mass are proportional to each other (F=ma) -If F increases, so does acceleration -Force causes acceleration -More force means more acceleration, same mass -More mass means less acceleration, same force Law of Conservation of Mass - -Mass can neither by created nor destroyed, only transformed Acceleration - --A change in velocity over time -Unites: USA-ft/s^2 and SI: m/s^2 Gravity - --Causes acceleration -Units: USA: 32.2 ft/s^2 SI: 9.8 m/sec^2 More than one force can be applied at a time on an object - -... Newton's Third Law - --For every action there is an equal and opposite reaction -Force -F=mg -Earth exerts a force on all of us Gravity - -Varies by location (on earth), distance (from earth), and mass (of planet) Mechanical Mechanical Weight - -Result of gravity acting on mass -The greater the mass, the greater the weight -Is a force -Units: lbs, N Work - -Result of a force moving an object against a resistance through some distance in a desired direction -Work transfers energy -Work is a measure of what is done and not the effort applied -Done by lifting, pushing, rotating, or sliding -W=Fd -F=Amount of force applied -d=Distance the object moves Power - -Tells us how fast work is done -Power varies with time (more power is needed to do work in less time, and less power is needed to do work in more time) -Power=Fd/s -Units: USA: ft-lb/s SI: watts (J/S) Force lets us do work on a system - -... System - -What we are studying Surroundings - -What we are not studying Closed System - -Energy may enter or leave. No mass enters or leaves the system i.e. Closed water bottle, car engine, human Open System - -Energy may enter or leave. Mass can enter or leave the system i.e. open water bottle, molecule, hydraulic cylinder, human Mechanics - -Mechanics is an application of math that describes how forces affect a body Statics - -Describes how applied forces bring a body into rest or equilibrium Dynamics - -Describes how applied forces bring a body into motion Vectors - --A quantity that has both magnitude and direction when placed within a coordinate system -Forces and Velocity i.e. driving 50 miles to the northeast Pythagorean Theorem - -a^2+b^2=c^2