Chapter 5 : Simple Machines: devices with few moving parts that make work easier. They can: Change direction of applied force or Change size of applied force or Change distance thru which force works.

Why Use Simple Machines? For the mechanical advantage… Makes something easier to do, but it takes a little longer to do it For example, going up a longer flight of stairs instead of going straight up a ladder

The 6 Simple Machines Screw Wedge Inclined Plane Pulley Wheel and Axle Lever

Definitions: Energy: Force: Ability to do work A Push or a Pull Work: Force (N) x Distance (m) if there is not a change in position, then no work is done So w = f d, f = w / d and d = w / f Work is measured in joules (J) or kilojoules (kJ)

Work input & output have to equal Work input is the amount of work done on a machine. Input force x input distance Work output is the amount of work done by a machine. Output force x output distance 15 m Wout = Win Fout x Dout = Fin x Din 10N x 3m = 2N x 15m Din Dout 3 m Fin 10 N

Input-Output Locations Input is where the effort force is applied Output is where the load is lifted or moved Mechanical advantage: # of times a machine multiplies your effort force. Use this formula: Mechanical advantage = resistance force / effort force OR MA = Fr / Fe

Levers A simple machine made of a bar that turns around a fixed point. Makes lifting weight easier by redirecting force over a different distance or changes direction of the force. https://www.primaryconnections.org.au/sites/all/modules/primaryconnections/includes/SBR/data/Phy/sub/levers/levers.htm

Parts of a Lever Fulcrum: fixed point Effort force, Fe: force applied by user Resistance force, Fr: force applied by object to be moved. Resistance (or load): is object to be moved.

First Class Lever Fulcrum is between Ef (effort) and Rf (load). Effort moves farther than Resistance. Multiplies Ef and changes its direction. Examples: claw end of hammer, seesaw, crowbar, scissors, pliers, your neck (cervical vertebrae)

Second Class Lever Rf (load) is between fulcrum and EF Effort moves farther than Resistance. Multiplies Ef, but does not change its direction Examples: nut crackers, wheel barrows, doors, and bottle openers. Also standing on your toes.

Third Class Lever Ef is between fulcrum and Rf (load) Resistance moves farther than Effort. Does not multiply force. Multiplies distance the effort force travels. Examples: tweezers, arm hammers, & shovels. Holding a weight in your hand with arm extended.

Levers in the Body

Pulley Pulley are wheels and axles with a groove around the outside Makes lifting things easier by redirecting force A pulley needs a rope, chain or belt around the groove to make it do work

Pulleys Examples: flag pole, elevator, sails, fishing nets, clothes lines, cranes, window shades and blinds, rock climbing gear

Diagrams of Pulleys Fixed pulley: Movable Pulley: A fixed pulley changes direction of force; does not increase F or create MA (so MA = 1). MA of a moveable pulley = the number of ropes that support the moveable pulley. Movable Pulley:

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. 

Inclined Planes An inclined plane is a flat surface that is higher on one end Inclined planes make the work of moving things up easier, but it increases distance A sloping surface, such as a ramp. An inclined plane can be used to alter the effort and distance involved in doing work, such as lifting loads. The trade-off is that an object must be moved a longer distance than if it was lifted straight up, but less force is needed. You can use this machine to move an object to a lower or higher place.  Inclined planes make the work of moving things easier.  You would need less energy and force to move objects with an inclined plane. 

Inclined Plane Egyptians used simple machines to build pyramids. A long incline made of dirt rose upward to the pyramid top gently. Blocks of stone were placed on large logs (another simple machine - wheel & axle) & pushed slowly up the inclined plane to the top of the pyramid.

Inclined Plane - Mechanical Advantage Mechanical advantage of an inclined plane = length of the slope height While plane gives MA, it does so by increasing the distance thru which the force must move.

Screw Turns rotation into lengthwise movement Takes many twists to go a short distance Holds things together Mechanical advantage of an screw is calculated by dividing the circumference by the pitch of the screw. The tighter the turns of the plane – the greater the MA.

Screw Examples: screws, bolts, clamps, jar lids, car jack, spinning stools, spiral staircases

Wedges Two inclined planes joined back to back. Wedges are used to split things, push them

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 The thinner the wedge, the higher the MA of the wedge. T

Wedge Examples: axe, doorstop, chisel, nail, saw, jackhammer, bulldozer, snow plow, horse plow, zipper, airplane wing, knife, bow of a boat or ship

WHEEL & AXLE Makes it easy to move things by rolling and reducing friction Examples: car, bicycle, office chair, fan shopping cart, hand truck, roller skates

WHEEL & AXLE The axle is stuck rigidly to a large wheel. Fan blades are attached to the wheel. When the axel turns, the fan blades spin.

Wheel & Axle The mechanical advantage of a wheel and axle is the ratio of the radius of the wheel to the radius of the axle. In the wheel & axle above, radius of the wheel is 5x larger than the radius of the axle. Therefore, MA is 5:1 or 5. The wheel & axle also increases speed by applying input force to the axle rather than to a wheel. The bigger the wheel is compared to the axle width, the greater the MA. 5 1

GEARS-Wheel and Axle Each gear in a series reverses the direction of rotation of the previous gear. The smaller gear will always turn faster than the larger gear.

Complex Machines Combining two or more simple machines to work together Examples: Car jack combines wedge and screw Crane or tow truck combines lever and pulley Wheel barrow combines wheel and axle with a lever

Rube Goldberg Machines Rube Goldberg machines are examples of complex machines. All complex machines are made up of combinations of simple machines. Rube Goldberg machines are usually a complicated combination of simple machines. By studying the components of Rube Goldberg machines, we learn more about simple machines

Safety Device for Walking on Icy Pavements When you slip on ice, your foot kicks paddle (A), lowering finger (B), snapping turtle (C) extends neck to bite finger, opening ice tongs (D) and dropping pillow (E), thus allowing you to fall on something soft.

Rube Goldberg Machine Examples https://www. youtube. com/watch Resources https://www.primaryconnections.org.au/sites/all/modules/primaryconnections/includes/SBR/data/Phy/sub/levers/levers.htm