Simple Machines

Spring 2014

Simple Machines

Inclined Plane• A plane is a flat surface. When that

plane is inclined, or slanted, it can help you move objects across distances and that's work! 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--a simple machine.

Wedge• You can use the edge of an inclined

plane to push things apart. Then, the inclined plane is a wedge. So, a wedge is actually a kind of inclined plane. An axe blade is a wedge. Think of the edge of the blade. It's the edge of a smooth slanted surface.

ScrewA screw an inclined plane wrapped

around a cylinder.

A screw can convert a rotational force (torque) to a linear force and vice versa.

Lever Any tool that pries something loose

is a lever. A lever is a rigid bar that "pivots" (or turns) against a "fulcrum" (or a fixed point).

Wheel and Axle It is two circular objects attached

together about a common axisWheel is the large cylinderAxle is the small cylinder

Pulley

In a pulley, a cord wraps around a wheel. As the wheel rotates, the cord moves in either direction. Now, attach a hook to the cord, and you can use the wheel's rotation to raise and lower objects.

Energy, Work, Power, & Machines

• 8.The mechanical advantage is the number of times a machine multiplies an effort force. Mechanical advantage can be calculated by the following equations:

• AMA = Fr IMA = de

Fe dr

• AMA = actual mechanical advantage (real life)• IMA = ideal mechanical advantage (pretend)• Fr = resistance force de = effort distance• Fe = effort force d r = resistance distance• 9. The mechanical advantage of a pulley

system is determined by counting the number of strands of rope that support the resistance force.

Energy, Work, Power, & Machines

• 10.Work input is always greater than work output due to friction.

Win= W out

Fe x de = Fr x d r

• Win = work input (J)• W out = work output (J)• Fe = effort force (N)• de = effort distance (m)• Fr =force of the resistance (N)• d r=how far the resistance moved (m)

Energy, Work, Power, & Machines• 11.Efficiency is a measure of how

much of the work put into a machine is changed to work put out by the machine.

• Efficiency is calculated using the following formula:

• efficiency = W out x 100%

Win

• efficiency = AMA x 100% IMA

Efficiency of a Machine12.The amount of work obtained from a

machine is always less than the amount of work put into it. This is because work is lost to friction.

Efficiency = output work / input work x 100Remember that work = force x distance

Energy, Work, Power, & Machines

• 13. Compound machines consist of two or more simple machines. A pencil sharpener is an example of a compound machine.