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.

Screw A 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 axis Wheel is the large cylinder Axle 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 Machine 12.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 100 Remember 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.