Science 5.0 Flashcards

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Mechanism

Mechanism

Made up of several different types of machines working together to perform a function.

Simple Machine

Machine that requires the application of a single force to do work. Examples: Ramps, levers, wedge, axle, pulley, wheel.

Six Simple Machines

Every machine is made up of at least one simple machine. A lever, wheel and axle, pulley, ramp, screw, or wedge.

Lever

Rigid bar that is supported at one point.

Fulcrum

The point on a lever where the bar is supported.

First-class lever

Lever that always has the fulcrum between the input and output forces. The output force is alwasys in the opposite direction to the input force.

Second-class lever

Lever where the output force is between the fulcrum and input force.

Third-class lever

Lever where the input force is between the output force and fulcrum.

Ideal Mechanical Advantage of a Lever Equation

Length of input arm / length of output arm

Human Levers

Many movements of the body can be exampled by comparing them with levers. Example: When a person throws a ball overhand, the elbow acts as the fulcrum of a first-class lever and the triceps muscle applies the input furce. The output force is the force that the hadn applies to the ball.

Pulley

Consists of a grooved wheel with a rope or caple looped around it.

Examples of pulleys

Flag poles, clotheslines, wells, and elavators.

Fixed pulleys

Pulleys that only change the direction of the force.

Ideal Mechanical Advantage of Pulley Systems

The IMA of a pulley system is equal to the number of support ropes. By counting the number of support ropes, you can find the IMA of a pulley system.

Wheel and axle

A large disk/wheel attached to a shaft or axle. Example: When you use a screwdriver to tighten a screw, the handle is the wheel, and the shaft is the axle.

Ideal Mechanical Advantage of a Wheel and Axle

If the input force is applied to the axle, the IMA - radius of the axle/radius of the wheel. If the input force is applied to the wheel, the IMA = radius of the wheel/radius of the axle.

Inclined Planes

A sloping surface on which an object can move.

Ideal Mechanical Advantage of an Inclined Plane

The IMA of an inclined plan is = Length of ramp / Height of ramp

Screw

An inclined plane wrapped around a rod.

Wedge

An inclined plan that travels through the object or material.

Mechanisms

A mechanism is a mechanical system that involves two or more simple machines working together.

Efficiency

Meaasures the useful work done by a machine compared to the work needed to operate it.

Useful Output Work

The work that the machine is designed to perform.

Work Done by Friction

Friction reduces the work and efficiency of a machine by converting some of the input work into heat, which is not useful for the intended output. To overcome friction, more work must be input into the machine.

Calculating Efficiency

Efficiency = Useful Outputwork (in joules) x 100% / input work (in joules)

How to Increase Efficiency

No machine has an efficiency of 100%, because some of the input work is used to compensate for the work done by friction. The best way to reduce friction is to use lubricant on any surfaces that touch (grease or oil), to fill the gaps between the surfaces, making it easier for those surfaces to slide past each other.

Example of increasing efficiency

One way to increase the efficiency of a device that produces thermal energy during the energy transfer is to lower the operating temperature of the device. This reduces the amount of energy that is wasted as heat and increases the amount of energy that is transformed into the useful output. For example, compact fluorescent lamps operate at a lower temperature than incandescent lamps and produce more light energy, because they operate at a lower temperature.