# Science lesson 20

### 26 terms by and4judge

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### work

The use of energy to apply a force to move an object. Work is defined as the amount of force multiplied by the distance the object moves.

### joule

The standard SI unit of energy, which is the ability to do work. It is defined as the energy used by a force of one newton moving an object a distance of one meter.

### simple machine

A device made up of one or two parts that reduces the effort neede to do work. It magnifies any applied force.

### lever

A rigid bar that picots about a fulcrum to multiply the force applied to one end.

### fulcrum

A fixed point that a lever pivots at.

### law of moments

For a lever with different amounts of weight on each side to be balanced, the distance that the first weight is from the pivot point multiplied by the weight, must equal the second weight multiplied by its distance from the pivot point. D(1)W(1)=D(2)W(2)

### torque

Torque is the turbning force acting on an object that is rotating or attached to a pivot point. It is the force multiplied by the distance of the force from the pivot point.

### first-class lever

A type of lever where the fulcrum is between the effort force, and the resistance force.

### effort

The force that is being applied to a machine, to produce work.

### effort arm

In a lever, it is the distance between the effort and the fulcrum.

### resistance

The force from the weight of the object we are trying to move with a simple machine.

### resistance arm

In a lever, it is the distance between the resistance and the fulcrum

### mechanical advantage

The property by which a simple machine multiplies an input force.

### second class lever

A type of lever where the resistance force is between the fulcrum and effot force.

### third-class lever

A type of lever where the effort force is between the fulcrum and the resistance force.

### wheel and axle

A simple machine that can be thought of as a lever that rotates in a circular manner aboutn and axle, which acts as a fulcrum.

### pulley

A type of simple machine compesed of a rope wrapped around a wheel.

### block and tackle

A system composed of two or more pulleys connected by ropes.

### distance principle

Using mechanical advantage to reduce the force necessary to move something will result in an increase inthe distance that the force acts.

### inclined plane

A simple machine that consists of a flat surface arranged at an angle so that one end is higher that the other.

### wedge

A simple machine that has inclined planes on two sides, that come to a point.

### screw

A simple machine made of an inclined plane wrapped around a shaft.

### pitch

1) the distance between the threads of a screw that determine its mechanicas advantage. 2) related to frequency, it is how high or how low our ears percieve a tone to be.

### efficiency

For a simple machine, it is output work divided by the input work.

### power

It is the rate at which work is perfomed, which is work done per unit of time, measured in watts.

### watt

The standard SI unit for power, defined as 1 joule per second.

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