GPS Standards S8CS5a: Observe and explain how parts can be related to other parts in a system such as the role of simple machines in complex (compound) machines. S8P3c: Demonstrate the effect of simple machines (lever, inclined plane, pulley, wedge. screw, and wheel/axle) on work.

What Are Machines? A machine is a tool used to make work easier. A machine is a tool used to make work easier. A simple machine is a machine that has very few moving parts A simple machine is a machine that has very few moving parts

There are six types of simple machines: - inclined plane- screw - wedge- pulley - wheel and axle- lever

Compound machines have two or more simple machines working together to make work easier

All compound machines are made of these simple machines

Examples of Compound Machines

Work Work is defined as a force acting on an object to move it across a distance. Work is defined as a force acting on an object to move it across a distance. Pushing, pulling, and lifting are common forms of work. Pushing, pulling, and lifting are common forms of work. Work involves 2 things: Force and Distance Work involves 2 things: Force and Distance Formula: Work = force (f) x distance (d)

Work Smarter NOT Harder According to the Law of Conservation of Energy: the amount of work put into a machine equals the amount of work that comes out According to the Law of Conservation of Energy: the amount of work put into a machine equals the amount of work that comes out Work Input = Work Output So how can machines make work easier?

GPS Standards S8CS5a: Observe and explain how parts can be related to other parts in a system such as the role of simple machines in complex (compound) machines. S8P3c: Demonstrate the effect of simple machines (lever, inclined plane, pulley, wedge. screw, and wheel/axle) on work.

Advantages of Using Simple Machines to do Work Simple Machines change : the size of the force the direction of the force the distance through which the force moves.

Advantages of Using Simple Machines to do Work Simple Machines can change the direction Simple Machines can change the direction of the force of the force Output force Input force

Advantages of Using Simple Machines to do Work Simple Machines can multiply the force thus changing its size, but the distance must also increase It’s a trade off! The amount of work stays the same. Takes less force to roll but longer distance Takes more force to lift but less distance

Effort and Resistance Force The effort force is the force that a person would put into the machine to move the object The resistance force is the force exerted by the load (the thing to be moved) in resistance to the effort

Mechanical Advantage (MA) How much easier and faster a machine makes your work is the mechanical advantage of that machine. In science terms, the mechanical advantage is the number of times a machine multiplies your effort force.

Mechanical Advantage (MA) To find the MA of a machine, you can divide the resistance force (output) by the effort force (input). Most of the time the resistance force is the weight of the object in Newtons. Formula: MA = F R / F E (F R = resistance force ; F E = effort force)

ALL SIMPLE MACHINES HAVE A MECHANICAL ADVANTAGE THAT HELPS US TO DO WORK

Inclined Plane A plane is a flat surface. When a plane is inclined, or slanted, it can help you move objects across distances. A common inclined plane is a ramp. Lifting a heavy box onto a loading dock is much easier if you slide the box up a ramp (an inclined plane) You trade a larger force for a longer distance Takes less force to roll but longer distance Takes more force to lift but less distance

MA of an Inclined Plane To find the MA of an inclined plane, divide its length by its height. MAI = length / height MAI = 12m / 6m MAI = 2

Calculate the MAI MAI = length / height MAI = 3000m / 100m MAI = 30

Wedges A wedge is a modification of an inclined plane that moves. It is made of two inclined planes put together. Instead of the resistance being moved up an inclined plane, the inclined plane moves the resistance. It changes the direction of the force

MA of a Wedge 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 MAW = S (slope) / T (thickness)

Screw A screw is an inclined plane wrapped around a post. Screw Thread

MA of a Screw The distance between two adjacent screw threads is called the pitch of a screw. One complete revolution of the screw will move it into an object a distance equal to the pitch of the screw. The mechanical advantage of a screw can be found by dividing the circumference of the screw by the pitch of the screw. This formula is shown below: MAS = Circumference / Pitch

LEVERS A lever is an arm that "pivots" (or turns) against a "fulcrum" (or point).

Parts of a Lever FULCRUM The fixed pivot point of a lever FULCRUM The fixed pivot point of a lever EFFORT ARM EFFORT ARM The part of a lever to which force is applied The part of a lever to which force is applied RESISTANCE ARM The part of the lever that bears the load or resistance RESISTANCE ARM The part of the lever that bears the load or resistance LOAD The object to be moved or the resistance to be overcome in order for work to be accomplished LOAD The object to be moved or the resistance to be overcome in order for work to be accomplished

Parts of a Lever

FIRST CLASS Examples of this kind of lever are : the pry bar, see- saw, hammer and pliers Examples of this kind of lever are : the pry bar, see- saw, hammer and pliers SECOND CLASS An example of this kind of lever is : the wheelbarrow and bottle opener. An example of this kind of lever is : the wheelbarrow and bottle opener. THIRD CLASS An example of this kind of lever is : fishing rod An example of this kind of lever is : fishing rod

They can be remembered by what is in the middle

MA of a Lever To find the MA of a lever, divide the effort arm length by the resistance arm length. MAL = effort arm length/resistance arm length

Pulleys When two or more pulleys are connected together, they allow a heavy load to be lifted with less force. The trade-off is that the end of the rope must move a greater distance than the load output force Input force A pulley is a rope or chain wrapped around a grooved wheel. A single pulley simply reverses the direction of a force.

Types of Pulleys Fixed Pulleys - pulleys attached to stationary structures A moveable pulley rises and falls with the load that is being moved. A single moveable pulley creates a mechanical advantage; however, it does not change the direction of a force. Pulleys can also multiply force. If you attach the pulley to the object that you are moving, the object will move one meter for every two meters the force pulls. A compound pulley is a moving pulley with a fixed pulley attached to it.

MA of a Pulley The mechanical advantage of a pulley is equal to the number of ropes that support the pulley. The mechanical advantage of a pulley is equal to the number of ropes that support the pulley.

Wheel and Axle Sometimes the wheel has a Sometimes the wheel has a crank or handle on it. crank or handle on it. Examples of wheel and axles include roller skates and doorknobs Examples of wheel and axles include roller skates and doorknobs A wheel and axle is a modification A wheel and axle is a modification of a pulley. of a pulley. It is a disk fixed to a shaft. The wheel It is a disk fixed to a shaft. The wheel and shaft must move together to be a and shaft must move together to be a simple machine. simple machine.

Examples of Items using a Wheel and Axle

MA of a Wheel and Axle The mechanical advantage of a wheel and axle is the ratio of the radius of the wheel to the radius of the axle. If the radius of the wheel is four times greater than the radius of the axle, every time you turn the wheel once, your force will be multiplied four times MAWA = Radius of wheel : Radius of axle

Mechanical Advantage (cont’) In the wheel and axle illustrated below, the radius of the wheel is five times larger than the radius of the axle. Therefore, the mechanical advantage is 5:1 or 5 In the wheel and axle illustrated below, the radius of the wheel is five times larger than the radius of the axle. Therefore, the mechanical advantage is 5:1 or 5

Machine Efficiency All machines waste some energy over- coming friction. Efficiency compares the output work to the input work. The less friction there is to overcome, the closer output work is to input work (the more efficient the machine is).

Machine Efficiency con’t. Efficiency is expressed as a percent (%). Formula: output work x 100 input work Sample Problem: A person does 1,500 J of work with a hammer. The hammer does 825 J of work on a nail, what is the efficiency of the hammer?

The Answer Efficiency = output x 100 input Efficiency = 825Jx J Efficiency = (0.55) x 100 = 55%