Work and Simple Machines ~ Chapter #3

For this set I recommend not doing the written format when studying and answering with definitions

Work

it is done on an object when you apply a force to it and it moves in the direction of that force. (J)

Work-Energy Theorem

the amount of energy is EQUAL to the amount of work

Kinetic Energy

energy due to motion

Potential Energy

stored energy (due to interactions between objects/particals)

Power

the rate at which work is done (W)

SI

scientific international (metric)

Machines

a device that makes work easier (does not reduce amount of work)

input force

the force which you push or pull on a machine

output force

force exerted on an object by a machine

input distance

the distance of the force you put on the machine

output distance

the distance of the force the machine exerts

three ways machines can make work easier to do

Can increase the size of the input force, making your force stronger (MA > 1). Can increase the distance over which your force acts, making your force last longer (MA < 1). Can change the direction in which a force is applied (MA = 1).

Mechanical Advantage (MA)

the ratio of a machine’s output force produced to the input force applied

Tradeoff

a machine can increase your input force but it goes over a shorter distance ==OR== increase the distance over which it acts, but it weakens you input force

Efficiency

is tthe ratio of the output work to input work (it is always less than 100%)

simple machine

A machine that does work with only one movement.

lever

A simple machine that consists of a rigid bar that pivots/rotates about a fixed point.

Frogs Lay Eggs mnemonic

Fulcrum, Load, Effort

fulcrum

The fixed point around which a lever pivots

input arm

the distance between the input force and the fulcrum

output arm

the distance between the output force and the fulcrum

1st class lever

The fulcrum in the middle (MA = anything)

2nd class lever

The load is in the middle (MA > 1)

3rd class lever

The effort force is in the middle (MA < 1)

Mechanical advantage is equal to one

the machine changes the direction of your input force.

Mechanical advantage is greater than one

the machine increases your input force, making it stronger

Mechanical advantage is less than one

the machine makes your input force last a longer distance

wheel and axle

an axle attached to the center of a wheel and both rotate together to increase your output force

inclined plane

a flat, sloped surface that makes lifting loads easier (increases our input force but makes us apply the force a longer distance)

wedge

a sloped surface that moves which helps us by cutting or separating two objects

screw

an inclined plane that is wrapped around a cylinder

pulley

a grooved wheel with a rope/chain/cable wrapped around it. (helps us lift loads and change the direction of force applied.)

fixed pulley

changes the direction of the force (MA = 1)

movable pulley

decreases the amount of input force needed to lift an object (MA = 1)

pulley system

A combination of fixed and movable pulleys (MA = 2)

compound machine

a machine that combines two or more simple machines (less efficient than simple machines at doing work)