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Physical Science > C7 Terms > Flashcards

C7 Terms Flashcards

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1
Q

Mechanical work (W)

A

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

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2
Q

Power (P)

A

The rate of doing work

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3
Q

watt (W)

A

1 joule of work done in one second

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4
Q

simple machine

A

Levers wheels axles and inclined planes

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5
Q

load/resistance

A

The system to be moved

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6
Q

resistance force (Fr)

A

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

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7
Q

effort force (Fe)

A

The force exerted

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8
Q

mechanical advantage (MA)

A

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

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9
Q

distance principle

A

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

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10
Q

lever

A

A bar that pivots about a fulcrum

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11
Q

fulcrum

A

A pivot point which a lever rotates on

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12
Q

rotational equilibrium

A

When the is no unbalanced force on a lever

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13
Q

moment/torque

A

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

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14
Q

moment arm (L)

A

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

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15
Q

law of moments

A

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

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16
Q

effort arm (Le)

A

The arm that takes the effort

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17
Q

resistance arm (Lr)

A

The arm that the load is on

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18
Q

first-class lever

A

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

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19
Q

second-class lever

A

When the resistance is between the effort arm and the fulcrum

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20
Q

third-class lever

A

When the effort is between the fulcrum and the resistance arm

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21
Q

wheel and axle

A

A wheel is usually a disk that rotates around an axis

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22
Q

gear

A

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

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23
Q

pulley

A

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

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24
Q

block and tackle

A

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

25
Q

inclined plane

A

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

26
Q

wedge

A

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

27
Q

screw

A

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

28
Q

thread count (TPI)

A

The number of threads in an inch

29
Q

pitch

A

The distance between adjacent threads on a screw

30
Q

What is the SI unit for work?

A

Joule

31
Q

What is the SI unit for power?

A

The watt

32
Q

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

A

Joules per second

33
Q

Two factors that determine power?

A

Force and time

34
Q

What are 3 categories of simple machines?

A

Levers wheels and axles or inclined planes

35
Q

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

A

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

36
Q

How does a simple machine provide a mechanical advantage?

A

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

37
Q

What does a simple machine not do?

A

Increase work output without increasing work input

38
Q

What is the distance principle?

A

The distance changes in proportion it the force

39
Q

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

A

False

40
Q

What are 2 essential parts of a lever system?

A

A bar and the fulcrum

41
Q

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

A

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

42
Q

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

A

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

43
Q

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

A

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

44
Q

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

A

False

45
Q

What is the major mechanical limitation of lever systems?

How can this limitation be overcome?

A

It will stop before one turn

Use a wheel or gear system

46
Q

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

A

Dividing the effort arm by the resistance arm

47
Q

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

A

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

48
Q

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

A

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

49
Q

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

A

True

50
Q

What is the general purpose of an inclined plane?

A

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

51
Q

How is the ideal MA of an inclined plane determined?

A

Divide the length by the hight

52
Q

What is the advantage of using an inclined plane?

A

It reduces the amount of force needed to move an object

53
Q

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

A

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

54
Q

Why is a double wedge sometimes necessary?

A

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

55
Q

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

A

By increasing the thread count you increase MA

56
Q

Section 7b

A

delete this card

57
Q

7c SQ

A

delete this card

58
Q

7d SQ

A

delete card

Physical Science (20 decks)

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