# Work, Power, and machines

## 46 terms

MA=work out ÷ work in

W=pt

W=fd

F=ma

m= f÷a

a= f÷m

F= w÷d

Joules

m/s²

Watts

Newtons

kilograms

### Newton's First Law

Objects remain at rest and objects in motion remain in motion unless acted upon by an unbalanced force

### Newton's Second Law

The acceleration of an object increases with increased force and decreases with mass

### Newton's Third Law

When an object exerts force on an another object, the second object exerts an equal opposite force onto the first object

A push or pull

### Centripetal force

A force that keeps an object moving in a circle

### Net Force

The overall forces combined

### Two ways to increase the acceleration of an object

Reduce mass and increase force

MA x 100

### How does a machine make work easier

Changes the direction
Changes the size of the force

### When is power increased

More work is done in a given amount of time
The time it takes to do work is decreased

### Examples of a lever

Wheelbarrow and scissors.

Ramp

Knife

Wagon

Jar Lid

Clothes Line

### Why are simple machines so useful?

The decrease the amount of work needed and have a mechanical advantage

### First Class Lever

A lever where the fulcrum is in the middle, the input force is on the left, and the resistance force (output force) is on the right

### Second Class Lever

A lever where the fulcrum is on the far left, the resistance force is on the right, and the input force is on the far right

### Third class lever

A lever where the fulcrum is on the far left, the input force is on the right, and the resistance force is on the far right.

### Input force

The force put on by the human

### Output force

the force done by the machine

### Examples of First Class Lever

See Saw, Scissors

Wheelbarrow

### Examples of Third Class lever

Fishing Rod, Catapult

Wheel and Axle

### Examples of Compound Machines

Can Opener, Scissors

### Compound Machines

A Machine that had two or more simple machines

### Lever

A Machine that has a fulcrum, or a bar that pivots at a fixed point

### Inclined Plane

A simple machine that is a straight, slanted surface

### Wedge

A double inclines plane that moves

### Screw

An inclines plane that is wrapped in a spiral

### Wheel and Axle

A simple machine consisting of two circular objects of different sizes

### Pulley

A simple machine consisting of a grooved wheel that holds a rope or cable

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