Mechanical systems Flashcards

1
Q

What do mechanisms do

A

they change the magnitude and direction of force

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2
Q

What are mechanical systems

A

systems that have mechanisms which transform an input motion and force into an output one

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3
Q

types of motion

A

linear
oscillating
rotary
reciprocating

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4
Q

what is linear motion

A

moving one way in a straight line

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5
Q

what is rotary motion

A

moving in a circle ( wheel)

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6
Q

what is reciprocating motion

A

moving backwards and forwards in a straight line such as a piston

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7
Q

what is oscillating motion

A

moving backwards and forwards in an arc motion, such as a swing

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8
Q

what do levers do

A

they move and lift loads by rotating around stationary points called fixed pivots/ fulcrum

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9
Q

what are levers

A

a rigid bar resting on a pivot/ fulcrum

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10
Q

summarise a first order lever

A
  • fulcrum or pivot in between effort and load
  • longer lever, less force required
  • e.g - scissors, grass cutters
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11
Q

summarise a second class lever

A
  • load in between fulcrum (Pivot) and effort
  • e.g. wheelbarrow, car door, nutcracker
  • the closer together the fulcrum and load, the easier to lift
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12
Q

summarise a third class lever

A
  • effort in between the fulcrum and load
  • moving the fulcrum and effort further apart makes the load easier to carry
  • e.g. fishing rods, chopsticks, tweezers
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13
Q

What do linkages do

A

change the magnitude of the force and direction of motion

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14
Q

Describe a push/pull linkage

A
  • use two fixed pivots
  • input and output motions of the linkage are in the same direction but the motion of the link arm is in the opposite direction
  • changing the position of the pivots will change the magnitude of output force
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15
Q

what do moving pivot points do

A

keeps link arm together

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16
Q

what do fixed pivot points do

A

keeps link arms parallel so anything put on won’t tip over

17
Q

Describe a bell crank

A
  • changes direction of force through 90 degrees
  • magnitude of output force can be changed by moving the fixed pivot so it’s not an equal distance between the two moving pivots
18
Q

Describe reverse motion linkage

A

changes direction of motion

the input and output don’t move in the same direction
used for foldable clothes horses

19
Q

Describe a crank and slider linkage

A
  • can change motion, e.g. oscillating to linear
  • the fixed pivot point anchors linkages to one place
  • the lever moves forwards and backwards in a slider
    -used in car engine
20
Q

What are gears

A

toothed wheels that interlock

21
Q

what do gears do

A

transfer motion from one part of a machine to another

22
Q

what is a gear train

A

where two or more gears are linked together

23
Q

what are gear trains used for

A

to change direction of motion/ change the magnitude of the input force

24
Q

What does the driver gear do

A

The driver and driven will turn in opposite directions when turned

25
What happens when you use a third gear (idler) with a driver and driven gear
the driver and driven gear will turn in the same direction, the size of the idler won't alter the speed of the other two gears
26
how does the size of a gear relate to the speed
a smaller gear or the one with fewer teeth will turn faster
27
how to find the gear ratio
gear ratio = number of teeth on the driven gear / number of teeth on the driver gear
28
how to find output speed
speed or driver gear (input speed) / gear ratio