Mechanical systems

Question 1

What do mechanisms do

Answer 1

they change the magnitude and direction of force

Question 2

What are mechanical systems

Answer 2

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

Question 3

types of motion

Answer 3

linear
oscillating
rotary
reciprocating

Question 4

what is linear motion

Answer 4

moving one way in a straight line

Question 5

what is rotary motion

Answer 5

moving in a circle ( wheel)

Question 6

what is reciprocating motion

Answer 6

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

Question 7

what is oscillating motion

Answer 7

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

Question 8

what do levers do

Answer 8

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

Question 9

what are levers

Answer 9

a rigid bar resting on a pivot/ fulcrum

Question 10

summarise a first order lever

Answer 10

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

Question 11

summarise a second class lever

Answer 11

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

Question 12

summarise a third class lever

Answer 12

• 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

Question 13

What do linkages do

Answer 13

change the magnitude of the force and direction of motion

Question 14

Describe a push/pull linkage

Answer 14

• 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

Question 15

what do moving pivot points do

Answer 15

keeps link arm together

Question 16

what do fixed pivot points do

Answer 16

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

Question 17

Describe a bell crank

Answer 17

• 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

Question 18

Describe reverse motion linkage

Answer 18

changes direction of motion

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

Question 19

Describe a crank and slider linkage

Answer 19

• 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

Question 20

What are gears

Answer 20

toothed wheels that interlock

Question 21

what do gears do

Answer 21

transfer motion from one part of a machine to another

Question 22

what is a gear train

Answer 22

where two or more gears are linked together

Question 23

what are gear trains used for

Answer 23

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

Question 24

What does the driver gear do

Answer 24

The driver and driven will turn in opposite directions when turned

Question 25

What happens when you use a third gear (idler) with a driver and driven gear

Answer 25

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

Question 26

how does the size of a gear relate to the speed

Answer 26

a smaller gear or the one with fewer teeth will turn faster

Question 27

how to find the gear ratio

Answer 27

gear ratio = number of teeth on the driven gear / number of teeth on the driver gear

Question 28

how to find output speed

Answer 28

speed or driver gear (input speed) / gear ratio