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Simple Machines and Mechanical Advantage (Lecture #4). ENGR 107 – Introduction to Engineering. Simple Machines. A mechanical device that changes the magnitude or direction of a force. Simple Machines. Simple Machines. The six classical simple machines are: Lever Wheel and axis Pulley
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ENGR 107 - Introduction to Engineering Simple Machines and Mechanical Advantage (Lecture #4) ENGR 107 – Introduction to Engineering
ENGR 107 - Introduction to Engineering Simple Machines
ENGR 107 - Introduction to Engineering A mechanical device that changes the magnitude or direction of a force. Simple Machines
ENGR 107 - Introduction to Engineering Simple Machines • The six classical simple machines are: • Lever • Wheel and axis • Pulley • Inclined plane • Wedge • Screw • All complex machines are constructed from one or more of these simple machines.
ENGR 107 - Introduction to Engineering Simple Machines • Simple machines can be classified as follows: • Those dependent on the vector resolution of forces • Inclined plane • Wedge • Screw • Those in which there is an equilibrium of torques • Lever • Pulley • Wheel
ENGR 107 - Introduction to Engineering Wheel and Axle
ENGR 107 - Introduction to Engineering Inclined Plane
ENGR 107 - Introduction to Engineering Simple Machines • A simple machine uses an applied force to do work against a load. • Work done on the load is equal to the work done by the applied force. • Can be used to increase the force acting on the load, at the expense of a proportional decrease in the distance that the load is moved. • The ratio of the force acting on the load to the force applied to the simple machine is known as the mechanical advantage.
ENGR 107 - Introduction to Engineering Mechanical Advantage
ENGR 107 - Introduction to Engineering The factor by which a simple machine multiplies the force or torque applied to it. Mechanical Advantage
ENGR 107 - Introduction to Engineering MA = output force / input force Mechanical Advantage applied force force acting on load
ENGR 107 - Introduction to Engineering MA = distanceapplied force / distanceload moved Mechanical Advantage
ENGR 107 - Introduction to Engineering WorkIN = WorkOUT Force applied x distanceapplied force = Force acting on load x distanceload moved Mechanical Advantage
ENGR 107 - Introduction to Engineering Pulley r1 r2 input output
ENGR 107 - Introduction to Engineering The tendency of a force to rotate an object about an axis, fulcrum or pivot. Torque (Moment)
ENGR 107 - Introduction to Engineering Torque (Moment)
ENGR 107 - Introduction to Engineering T = F x d Torque d = Distance measured from the point of rotation to the applied force F = applied force perpendicular to the measured distance
ENGR 107 - Introduction to Engineering MA = T2 / T1 = r2 / r1 Mechanical Advantage output input output input T = torque r = radius
ENGR 107 - Introduction to Engineering T2 = MA x T1 F2 x d2 = MA x (F1 x d1) F2 = MA x F1 x (d1 / d2) Mechanical Advantage
ENGR 107 - Introduction to Engineering Gears • Gears may be considered a simple machine. • Two or more gears working in tandem can produce a mechanical advantage. • Gear ratio • Unequal number of teeth • Gears in a transmission are analogous to wheels in a pulley.
ENGR 107 - Introduction to Engineering MA = T2 / T1 = #Teeth2 / #Teeth1 Mechanical Advantage output input output input T = torque #Teeth = # of teeth on gear
ENGR 107 - Introduction to Engineering Velocity Reduction
ENGR 107 - Introduction to Engineering VR = 1 / MA Velocity Reduction
ENGR 107 - Introduction to Engineering VR = T1 / T2 = r1 / r2 Velocity Reduction input output T = torque r = radius
ENGR 107 - Introduction to Engineering Pulley r1 r2 input output
ENGR 107 - Introduction to Engineering Gears r1 r2 input output
ENGR 107 - Introduction to Engineering A measure of the speed of rotation about an axis. Often specified in revolutions per minute (rpm). Angular Speed
ENGR 107 - Introduction to Engineering w2 = VR x w1 Angular Speed output input w1 = angular speed of input wheel or gear w2 = angular speed of output wheel or gear