C7 Terms

Question 1

Mechanical work (W)

Answer 1

When a force acts on an object to move it in a direction parallel to the force vector

Question 2

Power (P)

Answer 2

The rate of doing work

Question 3

watt (W)

Answer 3

1 joule of work done in one second

Question 4

simple machine

Answer 4

Levers wheels axles and inclined planes

Question 5

load/resistance

Answer 5

The system to be moved

Question 6

resistance force (Fr)

Answer 6

The least amount of force exerted on a load to begin moving it

Question 7

effort force (Fe)

Answer 7

The force exerted

Question 8

mechanical advantage (MA)

Answer 8

A measure of the reduction in effort to do a certain amount of work when using a simple machine

Question 9

distance principle

Answer 9

The distance a force must be exerted is directly proportional to the reduction of effort

Question 10

lever

Answer 10

A bar that pivots about a fulcrum

Question 11

fulcrum

Answer 11

A pivot point which a lever rotates on

Question 12

rotational equilibrium

Answer 12

When the is no unbalanced force on a lever

Question 13

moment/torque

Answer 13

When a force acts perpendicularly on a rotating around a pivot point it produces torque

Question 14

moment arm (L)

Answer 14

A mechanical moment is simply the product of a force and the distance from the pivot point where the force is applied

Question 15

law of moments

Answer 15

A lever will not move unless an unbalanced force acts on it

Question 16

effort arm (Le)

Answer 16

The arm that takes the effort

Question 17

resistance arm (Lr)

Answer 17

The arm that the load is on

Question 18

first-class lever

Answer 18

When the resistance and effort arms are on other side of the fulcrum

Question 19

second-class lever

Answer 19

When the resistance is between the effort arm and the fulcrum

Question 20

third-class lever

Answer 20

When the effort is between the fulcrum and the resistance arm

Question 21

wheel and axle

Answer 21

A wheel is usually a disk that rotates around an axis

Question 22

gear

Answer 22

A modified form of a wheel that has teeth around its circumference

Question 23

pulley

Answer 23

A wheel with a groove around its outer circumference and a rope or belt rest in the groove

Question 24

block and tackle

Answer 24

Two fixed pulleys and two moveable pulleys connected together in a gang by a single rope

Question 25

inclined plane

Answer 25

A two-dimensional tilted surface that allows a load to be moved with less effort

Question 26

wedge

Answer 26

A three-dimensional object that exerts a force to spread material apart as it is forced into the material

Question 27

screw

Answer 27

A long thin wedge wrapped around a shaft that can hold things together

Question 28

thread count (TPI)

Answer 28

The number of threads in an inch

Question 29

pitch

Answer 29

The distance between adjacent threads on a screw

Question 30

What is the SI unit for work?

Answer 30

Joule

Question 31

What is the SI unit for power?

Answer 31

The watt

Question 32

What is the SI equivalent for power in more basic terms?

Answer 32

Joules per second

Question 33

Two factors that determine power?

Answer 33

Force and time

Question 34

What are 3 categories of simple machines?

Answer 34

Levers wheels and axles or inclined planes

Question 35

What is always true about the ratio W out / W in?

Answer 35

The work out will not be 100% of the work in

Question 36

How does a simple machine provide a mechanical advantage?

Answer 36

It reduces the amount of force needed to do a given amount of work

Question 37

What does a simple machine not do?

Answer 37

Increase work output without increasing work input

Question 38

What is the distance principle?

Answer 38

The distance changes in proportion it the force

Question 39

T/F A simple machine allows you to accomplish a task with less work than if you did the work without the machine.

Answer 39

False

Question 40

What are 2 essential parts of a lever system?

Answer 40

A bar and the fulcrum

Question 41

What are the potential values of ideal MA for a 1st class lever? What is the relationship between effort and resistance in each case?

Answer 41

To be greater or less than 1 | If less than 1 the resistance moves more than the effort if greater than 1 the effort moves more than the resistance

Question 42

What are the potential values of ideal MA for a 2nd class lever? What is the relationship between effort and resistance in each case?

Answer 42

MA will always be greater than 1 which means that the effort will move more than the resistance

Question 43

What are the potential values of ideal MA for a 3rd class lever? What is the relationship between effort and resistance in each case?

Answer 43

MA will always be less than one which means that the resistance will move more than the resistance

Question 44

T/F The law of moments applies to a lever system under all conditions

Answer 44

False

Question 45

What is the major mechanical limitation of lever systems? | How can this limitation be overcome?

Answer 45

It will stop before one turn Use a wheel or gear system

Question 46

How is the ideal MA of a wheel axle system determined?

Answer 46

Dividing the effort arm by the resistance arm

Question 47

How is the ideal MA of a pair of gears determined?

Answer 47

Dividing the number of teeth on the resistance arm by the number of teeth on the effort arm

Question 48

Why is a pulley's minimum ideal MA = 1?

Answer 48

There is no possible configuration that would make the MA be less than one

Question 49

T/F The front wheel drive of a modern car is an example of a wheel-axle system?

Answer 49

True

Question 50

What is the general purpose of an inclined plane?

Answer 50

To reduce the effort required to move a object to a higher position

Question 51

How is the ideal MA of an inclined plane determined?

Answer 51

Divide the length by the hight

Question 52

What is the advantage of using an inclined plane?

Answer 52

It reduces the amount of force needed to move an object

Question 53

How does the height of a wedge determine how much force it can exert to cut or split?

Answer 53

Increasing the height if the width stays the same will increase MA

Question 54

Why is a double wedge sometimes necessary?

Answer 54

With out it the tip of the wedge may not be strong enough and break

Question 55

How does a screw's thread count or pitch determine how strongly it fastens and how hard it is to screw into a material?

Answer 55

By increasing the thread count you increase MA

Question 56

Section 7b

Answer 56

delete this card

Question 57

7c SQ

Answer 57

delete this card

Question 58

7d SQ

Answer 58

delete card