# Chpt. 5 Work and Machines

## 23 terms

### machine

a device that makes doing work easier

### input force

force that is applied to the machine (Fin stands for input force)

### output force

force applied by the machine (Fout stands for output force)

### input work

work done by you (example - applying work to a crowbar) (Win)

### output work

work done by the machine (example - the crowbar lifting a lid as you apply force on the crowbar) (Wout)

### work

is equal to force times distance
Fin Din = Fout Dout

the ratio of the output force to the input force

### efficiency

is a measure of how much of the work put into a machine is changed into useful output work by the machine.

### simple machine

machine that does work with only one movement

### lever

is a bar that is free to pivot or turn around a fixed point

### 1st class lever

the output force is always in the opposite direction to the input force

### 3rd class lever

the input force is applied between the output force and the fulcrum. the output force is always less than the output force.

### 2nd class lever

ithe output force is located between the input force and the fulcrum. the output force is always greater that the input force. the output force is exterted between the input force and the fulcrum.

### ideal mechanical advantage of a lever

IMA can be calculated for any machine by dividing the input distance by the output distance

### pulley

a grooved wheel with a rope, chain, or cable running along the grove. It can change the direction of the input force or increase input force, depending on whether the pulley is fixed or movable

### wheel and axle

a simple machine consisting of a shaft or axle attached to the center of a larger wheel.

### IMA of wheel and axle

radius of wheel divided by radius of axle

### inclined plane

a sloping surface such as a ramp that reduces the amount of force required to do work

### IMA of inclined plane

length of slope divided by height of slope

### screw

an inclined plane wrapped in a spiral around a cylindrical post

### wedge

an inclined plane with one or two sloping sides

### compound machine

two or more simple machines that operate together

### power

the amount of work done in the second