Simple Machines Chapter 5 There are six types of machines that scientists call 'simple machines.' 8/29/2018 Edwin P. Davis, M.Ed.

Levers Levers are one of the basic tools that were probably used in prehistoric times. Levers were first described about 260 BC by the ancient Greek mathematician Archimedes (287-212 BC). A lever is a simple machine that makes work easier for use; it involves moving a load around a pivot using a force. 8/29/2018

Lever The Lever: The lever is simply a bar supported at a single point called the fulcrum. The positioning of the fulcrum changes the mechanical advantage of the lever. 8/29/2018

Type 1 Lever the pivot (fulcrum) is between the effort and the load. 8/29/2018

1st Class Lever A first-class lever is a lever in which the fulcrum is located between the input effort and the output load. 8/29/2018

1st Class Levers Examples: Seesaw Trebuchet Crowbar Hammer Claw Hand trucks Pliers Scissors Shoehorn Spud bar Beam engine Wheel and axle. Chopsticks with hand 8/29/2018

Type 2 Lever the load is between the pivot (fulcrum) and the effort. 8/29/2018

2nd Class Lever In a second class lever the input effort is located at the end of the bar and the fulcrum is located at the other end of the bar, opposite to the input, with the output load at a point between these two forces. 8/29/2018

2nd Class Levers Dental elevator Nutcracker Paddle Curb bit Examples Dental elevator Nutcracker Paddle Curb bit Wheelbarrow Wrench Bottle opener Diving Board Crowbar Push-up Doorknob Nail clippers torsion spring 8/29/2018

Type 3 Lever the effort is between the pivot (fulcrum) and the load. : 8/29/2018

3rd Class Lever the input effort is higher than the output load, 8/29/2018

3rd Class Levers Examples Baseball bat Boat paddle Broom Electric Gates Fishing rod Hockey stick Mousetrap Shovel Stapler Tweezers Hammer Tennis racket The Human Arm 8/29/2018

Mechanical Advantage The ratio of the output force to the input force is the mechanical advantage of a machine. The mechanical advantage of a machine can be calculated from the following equation. 8/29/2018

Mechanical Advantage (MA) the factor by which a mechanism multiplies the force or torque put into it. :                           8/29/2018

Mechanical Advantage of the Levers To find the MA of a lever, divide the effort arm length by the resistance arm length. MA = effort arm length / resistance arm length 8/29/2018

Pulley A pulley consists of a grooved wheel that turns freely in a frame called a block. A pulley can be used to simply change the direction of a force or to gain a mechanical advantage, depending on how the pulley is arranged. 8/29/2018

Examples of Pulleys                                                                                                                                                                                                                                                                                                                                                                                                                                     8/29/2018  

Can you name all the pulleys? block and tackle rock climber pulleys winch oil derrick clothesline pulley marine pulley steam shovel flagpole pulley window blinds 8/29/2018

Fixed Pulley A fixed or class 1 pulley has a fixed axle. That is, the axle is "fixed" or anchored in place. A fixed pulley is used to change the direction of the force on a rope (called a belt). A fixed pulley has a mechanical advantage of 1. A pulley is said to be a fixed pulley if it does not rise or fall with the load being moved. A fixed pulley changes the direction of a force; however, it does not create a mechanical advantage 8/29/2018

Fixed Pulley "fixed" or anchored in place. 8/29/2018

Movable Pulley A movable or class 2 pulley has a free axle. That is, the axle is "free" to move in space. A movable pulley is used to multiply forces. A movable pulley has a mechanical advantage of 2. The mechanical advantage of a moveable pulley is equal to the number of ropes that support the moveable pulley. (When calculating the mechanical advantage of a moveable pulley, count each end of the rope as a separate rope). 8/29/2018

Movable Pulley the axle is "free" to move in space. 8/29/2018

Diagrams of Pulleys Fixed pulley: Movable Pulley: A fixed pulley changes the direction of a force; however, it does not create a mechanical advantage. Fixed pulley: The mechanical advantage of a moveable pulley is equal to the number of ropes that support the moveable pulley. Movable Pulley: 8/29/2018

Block and Tackle Compound A compound pulley is a combination of a fixed and a movable pulley system. - A block and tackle is a compound pulley where several pulleys are mounted on each axle, 8/29/2018

Block & Tackle 8/29/2018

COMBINED PULLEY The effort needed to lift the load is less than half the weight of the load. The main disadvantage is it travels a very long distance.  8/29/2018

Mechanical Advantage of Pulleys An example of a rope and pulley system illustrating mechanical advantage . 8/29/2018

Inclined Plane The Inclined Plane: Often referred to as a 'ramp' the inclined plane allows you to multiply your force over a longer distance. In other words, you exert less force but for a longer distance. You do the same amount of work, it just seems easier because you spread it over time. 8/29/2018

Examples of Inclined Plane An inclined plane lifts the front of this car.                              An inclined plane is used to lift this heavy wheelbarrow into this trailer. A short ramp is needed to equal these two steps. 8/29/2018

Mechanical Advantage - Inclined Plane The mechanical advantage of an inclined plane is equal to the length of the slope divided by the height of the inclined plane. While the inclined plane produces a mechanical advantage, it does so by increasing the distance through which the force must move. 8/29/2018

Wedge The Wedge: A wedge works in a similar way to the inclined plane, only it is forced into an object to prevent it from moving or to split it into pieces. A knife is a common use of the wedge. 8/29/2018

Examples of Wedges A door stop is a wedge that stops the door from moving.                         The sharp edge of an ax is a wedge. The sharp edge of the shovel is a wedge. 8/29/2018

Wedge – Mechanical Advantage The mechanical advantage of a wedge can be found by dividing the length of either slope (S) by the thickness (T) of the big end. S As an example, assume that the length of the slope is 10 inches and the thickness is 4 inches. The mechanical advantage is equal to 10/4 or 2 1/2. As with the inclined plane, the mechanical advantage gained by using a wedge requires a corresponding increase in distance. T 8/29/2018

Screw The Screw: The screw is really just an inclined plane wrapped around a rod. It too can be used to move a load (like a corkscrew) or to 'split' and object (like a carpenter's screw). 8/29/2018

Examples of Screws                     Some screws have a sharp point and are mostly used on wood.                  Light bulbs have threads to screw them into sockets                  The faucet has threads to screw the hose on. 8/29/2018

Efficiency Efficiency is a measure of how much of the work put into a machine is changed into useful output work by the machine. A machine with high efficiency produces less heat from friction so more of the input work is changed to useful output work. 8/29/2018

Calculating Efficiency To calculate the efficiency of a machine, the output work is divided by the input work. Efficiency is usually expressed as a percentage by this equation: 8/29/2018

Wheel & Axles The wheel and axle is a simple machine. A wheel and axle is a lever that rotates in a circle around a center point or fulcrum. The larger wheel (or outside) rotates around the smaller wheel (axle). 8/29/2018

Wheel & Axles A wheel is a lever that can turn 360 degrees and can have an effort or resistance applied anywhere on that surface. The effort or resistance force can be applied either to the outer wheel or the inner wheel (axle). 8/29/2018

Examples of Wheel & Axle 8/29/2018

Wheel and Axles pencil sharpener casters door knobs rolling pin rotary dial telephone  egg beater bicycle fan windmill roller skates record player wagon 8/29/2018

Mechanical Advantage The mechanical advantage of a wheel and axle machine can be found by dividing the radius of the wheel by the radius of the axle. Mechanical Advantage (M.A) = radius of the wheel / radius of the axle 8/29/2018