Engineering Simple Machines

Engineering Simple Machines

Essential Question:

How do simple machines make life easier for us?

What is Work?

Work is when an applied force causes an object to move in the direction of the force.

Work Illustration...

It is not work...

Work is done only when an object moves in the same direction of the force that is being applied.

Suppose you try to push a brick wall over. 

• Is this considered work? 

• Why or why not?

Work Formula

Work = Force x distance

W = F x d

A machine is a device that makes work easier by changing the size or direction of a force.

Look at the list below and identify which are considered machines:

• Can Opener

• Door Knob

• Brake

• Knife

Machines

• There are simple machines and complex machines

• Complex machines have 2 or more simple machines

• There are six (6) types of simple machines: inclined plane, wedge, screw, lever, pulley, and wheel and axle

Inclined Plane

• Straight, slanted surface

• Makes work easier because it is easier to move something to a higher or lower place

Wedge

• Inclined plane that moves

• Two inclined planes joined back to back

• Wider or thicker at one end than at the other

• Makes work easier because when moved, a wedge cuts, splits, or pries apart objects (including air and water)

Screw

• Inclined plane wrapped around a cylinder with a wedge at the tip

• Makes work easier because it applies lots of force with little effort

• Makes work easier because it is used to hold things together

Additional Screw Info

• More threads on a screw make it easier to turn, but it takes longer

• A screw might be called a complex machine because it has both an inclined plane and a wedge at its tip

Lever

• Made up of a bar that pivots at a fixed point called a fulcrum

• Force applied to a lever is called the effort

• Object moved is the load

Three (3) Classes of Levers

• In a first class lever the fulcrum is in the middle and the load and effort is on either side

• In a second class lever the fulcrum is at the end, with the load in the middle

• In a third class lever the fulcrum is again at the end, but the effort is in the middle

What is the relationship between the location of the fulcrum in a lever and effort?

The closer the fulcrum is to the load, the less effort you will need

Wheel and Axle

• Consists of two circular objects of different sizes

• A wheel is connected to a post (axle)

• Wheel is larger than the axle

• Makes work easier because it applies more force or lifts a heavy load with less effort 

Pulley

• Wheel and axle with a groove around the outside

• A pulley needs a rope, chain or belt around the groove to make it do work

• Pulley systems can consist of one or more fixed pulleys, one or more moveable pulleys, or both fixed and movable pulleys

• Makes work easier by changing the direction of the force or multiplying the effort used

Complex Machines

Simple Machines can be put together in different ways to make complex machines