ASVAB Mechanical Comprehension

force

mass × acceleration

vector quantities

forces that has both size and direction

equilibrium

a stable situation in which forces cancel one another

velocity

the speed and direction of a moving object

acceleration

the rate at which velocity changes

pressure

force (in pounds) ÷ area (in inches)

work

force × distance

tension is measured in

pounds-force or newtons

work is measured in

foot-pounds

power

work ÷ time

power is measured in

horsepower (hp)

1 horsepower

33,000 foot-pounds per minute or 550 foot-pounds per second

mechanical advantage

when a machine multiplies the force you use

mechanical advantage

resistance ÷ effort = output force ÷ input force

fulcrum

point of support to reduce resistance and multiply the effect of effort

resistance arm

the part of a lever that applies a force on an object

effort arm

the part of a lever that you apply an input effort force to.

to determine how much a lever reduces the amount of effort needed to do work

length of effort arm ÷ length of resistance arm = resistance force ÷ effort force

mechanical advantage of using a lever

effort arm ÷ resistance arm

mechanical advantage of using a ramp

length of ramp ÷ height of ramp = weight of object being moved ÷ force required to move object

block and tackle pulleys

make lifting heavy objects easier or change the direction of the pull

a simple pulley

force must equal the weight of the object

gears

used to change direction, increase or decrease speed, or increase or decrease force

if you have an even number of gears connected in a series

the first and last gear turn in opposite directions

if you have an odd number of gears connected in a series

the first and last gear turn in the same direction

number of teeth

the speed at which a gear rotates depends on the ______

bevel gears

used to connect gears that have shafts (that aren't parallel to one another) at different angles

drive other pulleys

when connected by a system of belts, pulley can do what?

diameter of the pulley in relation to the diameter of the pulley that's driving it

how fast a pulley rotates depends of what?

wheel and axle

multiplies the effort used producing a greater force

wheel and axle

are fixed together and turn at the same time; ex. using a steering wheel

wheel and axle mechanical advantage

the relationship between the radius of the wheel and the radius of the area to which force is being applied

pitch

the distance between the ridges of the spiral (on the screw of a vise) is called the _____ of the thread

greater

the ____ the pitch of the thread, the farther the jaws of the vice move for each revolution of the handle

more

larger pitches require ____ force to rotate the handle than screws with smaller pitches do

hydraulic jack

uses a nearly incompressible liquid, such as oil, to exert force in order to move an object

mechanical advantage of a hydraulic jack

the ratio between the diameters of the two cylinders