Directed Reading: What is a Machine? and Types of Machines

what is a device that makes work easier by changing the size or direction of force

a machine

a machine that is made of two or more simple machines

compound machine

a machine that has a mechanical advantage of less than 1 reduces the output force but can increase the _____________ an object moves.

distance

what is the formula for finding mechanical advantage

output force divided by input force

in a machine that has a mechanical advantage of more than 1 the ______ force is greater than the _____ force

output/input

what type of common machine is a screwdriver that is used to pry off the lid on a paint can

a lever

why do machines need less force to do the same amount of work

because machines allow force to be applied over a greater distance

in a second-class lever, why must you exert input force over a greater distance?

because the output force is greater than the input force

how do you find the mechanical advantage of a wheel and axle

by dividing the radius of the wheel by the radius of the axle.

name three examples of everyday machines

cars, big construction equipment, computers

when a machine changes the size of the force, the _________ through which the force is exerted must also change

distance

why is it impossible to build an ideal machine

every machine has moving parts

When you use the claw end of a hammer to remove a nail, what type of simple machine are you using?

first class lever

where are the fulcrum, the load, and the input force located in a first-class lever, a second-class lever, and a third-class lever?

first class: fulcrum is between the input force and the load, second class: the load is between the fulcrum and the input force, third class: the input force is between the fulcrum and the load

Which type of pulley is attached to something that does not move?

fixed pulley

when a machine drills holes in metal, some of the work input is used to overcome _____________ between the metal and drill

friction

What would a machine that had 100% mechanical efficiency be called?

ideal machine

a simple machine that is straight, slanted surface, which facilitates raising a load

inclined plane

a ramp will decrease the size of the input force needed to lift a box and __________ the distance over which the force is exerted

increases

What do first-class levers always change the direction of?

input force

when a screwdriver is used to open a can, both the size and direction of the ____________ change

input force

a simple machine with a bar that pivots at a fixed point is a

lever

What do some machines use to lower friction between moving parts?

lubricants ; oil & grease

what is the number of times a machine multiplies force called?

mechanical advantage

what is the quantity that measures the ratio of work output to work input called

mechanical efficiency

Which type of pulley is attached to the object being moved?

movable pulley

what determines the mechanical advantage of a block and tackle?

number of rope segments

what simple machine has a grooved wheel that holds a rope or cable

pulley

a simple machine that consists of an inclined plane wrapped around a cylinder

screw

the three classes of lever are based on the location of what three features

the fulcrum, the load, and the input force

What are the six simple machines that all other machine are made from

the lever, inclined plane, wedge, screw, pulley, and the wheel and axle

how does a movable pulley move

they are attached to the object being moved

Why is the output force always less than the input force in a third-class lever?

third class levers do not increase the input force

what does a wheel and axle consist of

two circular objects of different sizes

A knife is actually a very sharp

wedge

a simple machine that is made up of two inclined planes and that moves

wedge

what kind of simple machine is a faucet

wheel and axle

describe a block and tackle

when a fixed pulley and a movable pulley are used together

The work you do on a machine is called

work input

Work output can never be greater than

work input

the work done by a machine on an object is called?

work output

what is the equation for finding mechanical efficiency

work output / work input x 100

what is the fixed point on a lever called

fulcrum

how does a fixed pulley affect force

It changes the direction of force