# Science Chapter 4: Work and Machines Study Guide

## 20 terms · Missing a few but they will be added

### Efficiency

The percentage of the input work that is converted to output work

### Fulcrum

the fixed point around which a lever pivots

### Inclined Plane

a flat surface with one end higher than the other

### Input Force

the force exerted on a machine

### Output Force

the force exerted on an object by a machine

### Joule

a unit of work equal to one Newton-meter

### Lever

a simple machine that gives a mechanical advantage when given a fulcrum

### Machine

a device that changes the amount of force exerted or the direction in which force is exerted

the number of times the force exerted on a machine is multiplied by the machine

### Pulley

A grooved wheel around which is wrapped a rope, chain, or cable

### Screw

an inclined plane wrapped in a spiral around a cylindrical post

### Wedge

an inclined plane that moves

### Wheel and Axle

a simple machine made of two circular or cylindrical objects fastened together that rotate about a common axis.

### Work

force exerted on an object that causes it to move

### When does one know when work is being done on an object?

When the force on an object causes it to move in a given direction.

### How do you figure out the efficiency of a machine?

Divide output work by input work and multiply by 100%; (OUTPUT Work/INPUT Work)x100%

### How do you find out the mechanical advantage of a machine?

Divide output work by input work;OUTPUT Work/INPUT Work (Note: No unit)

### What is a compound machine?

2 or more simple machines put together to perform a simple task

### How are the 3 classes of levers arranged and what do they do?

1) First Class Lever: Multiply force, changes direction 2) Second class levers: Multiply force, no direction change 3) Third Class Lever: Multiply distance, no direction change

### What are 3 things machines do?

Machines: Change the amount of force exerted; Change the distance over which force is exerted; Change the direction in which force is exerted