Mechanical Flashcards
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:
Intake
Compression
Combustion
Exhaust
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
