Chapter 12 Section 2

shorter

*a machine multiplies distance to make work easier* example: in some machines, the *output force is less than the input force*: the advantage is that it allows you to exert your input force over a _______ distance than you would without the machine (on a bike you apply a large force to the pedals over a short distance but the bike still moves a longer distance)

machine

a device with which you can do work in a way that is easier or more effective

divide/multiply

to calculate the efficiency of a machine: ________ the output work by the input work and ________ the result by 100% (____/____)

distance

when you do work with a machine, you exert a force over some ________

ratio`

Finding the _____ of output force to input force gives you the mechanical advantage of a machine

mechanical advantage

Finding the ratio of output force to input force gives you the _________ _________ of a machine

less

For a machine that *multiplies distance*, the mechanical advantage is ______ than 1

greater

For a machine that *multiplies force*, the mechanical advantage is_______ than 1

1

For a machine that changes direction, the mechanical advantage will be __ (answer in number form)

same

For a machine that changes direction: if only the direction changes, the input force will be the _______ as the output force

greater

For a machine that multiplies force the output force is greater than the input force

true

In real situations, the output work is *always* less than the input work (true or false?)

actual mechanical advantage

The mechanical advantage that a machine provides in a real situation is called the ________ ___________ ___________

increase

*a machine multiplies force to make work easier* example: in some machines, the *output force is greater than the input force* example: How can you exert a smaller force than is necessary for a job if the amount of work is the same? (think of a shovel) If the amount of work stays the same, a decrease in force must mean an _______ in distance So if a machine allows you to use less force to do some amount of work, you must apply the input force over a greater distance. In the end, you do as much work with the machine as you would do without the machine, but the work is easier to do

multiplying/changing

A machine makes work easier by _______(ing) force or distance, or by ______(ing) direction (answer: _____/____)

amount

A machine makes work easier by changing the _______ distance, or direction of force you exert

distance

A machine makes work easier by changing the amount _______, or *direction* of force you exert

direction

A machine makes work easier by changing the amount distance, or ________ of force you exert

mechanical advantage

A machine's ________ ________ is the number of times a force exerted on a machine is multiplied by the machine

true

You cannot predict the actual mechanical advantage of a machine (true or false?)

direction

a machine changes ________ to make work easier example: think about raising a sail you could raise the sail by climbing the mast of the boat and pulling up on the sail with a rope. But it is easier to stand on the deck and pull down than to lift up. By running a rope through the top of the mast as shown (on page 380 Figure 7), you can raise the sail by pulling down on the rope. This rope system makes your job easier by changing the direction in which you exert your force

true

the more efficient a machine is, the closer the actual mechanical advantage is to the ideal mechanical advantage (true or false?)

percent

efficiency is expressed as a ________

higher

efficiency is expressed as a percent. So the _________ the percent, the more efficient the machine is

friction

in real situations, the output work is always less than the input work because (in any machine) some work is wasted overcoming _________

resistance (because the machine must overcome some resistance)

sometimes output force is called ________ force

less

the ______ friction there is, the closer the output work is to the input work

efficiency

the __________ of a machine compares the output work to the input work

output force

the force exerted by the machine

input force

the force you exert on the machine

effort

the input force is sometimes called the ______ force

ideal mechanical advantage

the mechanical advantage of a machine *without friction*

actual

the more efficient a machine is, the closer the _______ mechanical advantage is to the ideal mechanical advantage

ideal

the more efficient a machine is, the closer the actual mechanical advantage is to the ______ mechanical advantage