The only type of pulleys that provide mechanical advantage

Moveable pulleys

Formula for gear revolutions

r x d = R x D

r = revolutions

d = # of teeth

r/d = Gear A

R/D = Gear B

Hydrometers use ______ to measure ________.

Hydrometers use **floats **to measure **specific gravity**.

Specific gravity

Specific gravity is the ratio of the **density of a substance** to the **density of a reference substance.**

In a hydrometer, the liquid with the ________ _________ ________ will cause the float to rise higher in the glass tube.

In a hydrometer, the liquid with the **highest specific gravity** will cause the float to rise higher in the glass tube.

First-class lever

Fulcrum is in the middle

E.g. scissors, pliers

Second class lever

Fulcrum is at one end, load is in middle

E.g. nutcracker, wheelbarrow

Third class lever

Fulcrum is at one end, effort is in between

E.g. tongs, tweezers

When spinning together, which pulley spins faster, the small or large one?

The small one -- it has to keep up

Formula for mechanical advantage in pistons

(Smaller displacement)/(Larger displacement) = MA

a1 x d1 = a2 x d2

a = area

d = displacement

An axe is, in mechanical terms:

A wedge, i.e. an inclined plane.

Voltimeter

Tells the total voltage in a circuit.

Is a burnt-out light bulb a circuit?

No, but a voltimeter can bypass it if connected to both ends.

In an electrical series, current and voltage do what?

Current stays constant, voltage does not.

In an electrical parallel

Current changes; voltage does not.

Formula for voltage

V = I x R

Voltage = (current) x (resistance)

A series has greater resistane because its current must pass through _______.

**resistors**

In a 2-pulley system, the movable pulley will only move up _________ the distance and spin ________ as much as the fixed pulley.

In a 2-pulley system, the movable pulley will only move up **half **the distance and spin **half **as much as the **fixed **pulley.

To find RPM of wheel with rods:

Take the **needed contacts per minute** and divide that by the **# of rods** on the wheel.

E.g. need 120 contacts per minute, have 10 rods =

120/10 =

**12 RPM**

The closer to the center of a driver wheel that an adjacent wheel is present, the _______ it will move.

The closer to the center of a driver wheel that an adjacent wheel is present, the **faster **it will move.

The deeper you go underwater with an inflated ball, the more _______ it becomes.

The deeper you go underwater with an inflated ball, the more **buoyant **it becomes.

Rate of heat exchange is ______ through objects of greater temperature difference.

Rate of heat exchange is **faster **through objects of greater temperature difference.

If you place an object evenly on 2 scales, each scale will read _______ of the total weight.

If you place an object evenly on 2 scales, each scale will read **half **of the total weight.

The 4 strokes of a 4-stroke engine:

**I**ntake

**C**ompression

**C**ombustion

**E**xhaust

Formula for mechanical advantage in wheel and axle:

MA = (radius of wheel) / (radius of axle)

Formula for pressure:

Pressure = force x area

Formula for momentum

Momentum = force x distance

Potential energy

Energy stored in an object

Formula for electrical current

I = Q / T

Current (I) = Charge (Q) / Time (T)

Ammeter

Measures current flow in a circuit

Voltmeter

Measures voltage

Multimeter

Measure both current and voltage

Unit for charge

Q

coulomb

Formula for power

Power = volts x amperes

Newton's First Law

Objects in motion tend to stay in motion; objects at rest tend to stay at rest.

Newton's Second Law

Force = (mass) x (acceleration)

Newton's Third Law

For every action, there is an **equal and opposite** reaction.

Formula for weight

Weight = mass x gravity

Convection (of heat)

Occurs in liquids and gases by **circulating currents **caused by **difference in density**.

Conduction (of heat)

occurs **in solids** and **in stationary fluids**;

**temperature difference** between objects effects rate.

What does placing salt in water do to the water's __specific gravity__ and __freezing point__?

It **increases **the specific gravity and **lowers **the freezing point.

Heat moves

always from hot object to cold object

Compressing air in a closed place does what to volume and temperature?

decreases volume and raises temperature

Alphabet for current

I

Alphabet for charge

q

Ampere (amp)

Electric current (I)

Ohm

Resistance (R)

Watt

Electric power (P)

Coulomb

Electric charge (Q)

Joule

Energy (E)

Hertz

Frequency (f)

Apparent specific gravity

the ratio of the **weight **of a volume of the substance to the **weight **of an equal volume of the reference substance