Mechanical Devices and Electronical Systems

Question 1

Define

mechanism.

Answer 1

a series of parts that work together to control forces and motion

Question 2

Define

system.

Answer 2

the general name for a set of mechanical or electronic parts that work together to produce a desired ouput

Question 3

Define

force.

and give its units.

Answer 3

a push, a pull or a twist

measured in newtons (N)

Question 4

What is

rotary motion?

and what is it measured in?

Answer 4

motion that follows the path of a circle
e.g. rotation of wheels

it is commonly measured in revolutions per minute (rpm)

Question 5

What is the equation for

speed?

Answer 5

speed = distance/time

Question 6

What is

oscillating motion?

and what is it measured in?

Answer 6

similar to circular motion, but the rotation moves back and forth in a circular path
e.g. an electric toothbrush head

it is measured in oscillation per second (or per minute)

Question 7

What is

reciprocating motion?

and what is it measured in?

Answer 7

back-and-forth motion in a straight line

it is measured in oscillations per second (or per minute)

Question 8

Define

input.

(in terms of motion)

Answer 8

the type of motion put into a mechanism

Question 9

Define

output.

(in terms of motion)

Answer 9

the type of motion a mechanism produces

Question 10

Define

lever.

Answer 10

a rigid bar that turns around a fulcrum

Question 11

Define

fulcrum.

Answer 11

the pivot around which a lever turns

Question 12

Define

effort.

Answer 12

the input force

Question 13

Define

load.

Answer 13

the output force

Question 14

Define

arm length.

Answer 14

the distance between the force being exerted and the fulcrum

Question 15

Define

torque.

Answer 15

a turning or twisting force

Question 16

What can

rotary mechanical systems do?

(2 things)

Answer 16

• reduce rotary speed but increase torque
• increase rotary speed but reduce torque

Question 17

Define

cam and follower.

Answer 17

a mechanism to convert rotary motion into reciprocating motion

Question 18

How does a

cam and follower work?

Answer 18

A cam is a specially shaped wheel
The follower rests on the edge of the cam.

As the cam rotates, the follower moves up and down.

Question 19

Define

spur gear.

Answer 19

a wheel with teeth around its edge

Question 20

Define

simple gear train.

Answer 20

a pair of gears consisting of a driver gear and a driven gear

Question 21

Define

pinion.

Answer 21

a small driver gear

(smaller than the driven gear)

Question 22

Define

shaft.

Answer 22

a rod that transfers the rotation through a mechanism

Question 23

What are the

two key rules for gears of different sizes?

Answer 23

• the smaller gear will rotate faster than the larger gear
• the gears will rotate in opposite directions

Question 24

Define

lubrication.

Answer 24

a substance applied to reduce friction between moving parts

Question 25

# Define pulley and belt drive.

Answer 25

a method of transferring rotary motion between two shafts

Question 26

# What are the two characteristics of pulley and belt drives | that are different to simple gear trains?

Answer 26

- the input shaft and the output shaft can be separated by a greater distance in pulley and belt drives - the input and output shafts rotate in the same direction in pulley and belt drives

Question 27

# Define linkage.

Answer 27

a component used to direct forces and movement to where they are needed

Question 28

# Define subsystem.

Answer 28

a section with a specific role within a system

Question 29

# Define system diagram.

Answer 29

a diagram of the interconnections and flow of signals in an electronic system

Question 30

# Define sensor.

Answer 30

a component that produces a signal in response to a specific physical quantity

Question 31

# Define physical quantity.

Answer 31

something that can be measured | e.g. light, speed, temperature

Question 32

# Define signal.

Answer 32

an electrical voltage that is used to represent information

Question 33

# Define microcontroller.

Answer 33

a programmable electronic component that adds functionality to a product

Question 34

# Define program.

Answer 34

a set of instructions to tell a microcontroller how to carry out a task

Question 35

# Define embedding.

Answer 35

customising a microcontroller to be permanently placed within a product

Question 36

# What are some examples of input sensors? | (3)

Answer 36

- light sensor - infrared sensor - switch sensor

Question 37

# How does a LDR (light sensor) work?

Answer 37

it produces a signal that rises when the light level increases

Question 38

# What are the two different types of infrared sensors? | and how do these work?

Answer 38

- simple IR sensor - produces a signal when it detects a warm object within range - passive infrared sensor (PIR) - detects a moving warm object

Question 39

# What are switch sensors?

Answer 39

very simple electronic components that can either be off or on

Question 40

# What are some different types of switches available? | (4)

Answer 40

* latching push switch * tilt switch * momentary push switch * time delay switch

Question 41

# Define latching switch.

Answer 41

a switch that stays on (or off) after the button is released

Question 42

# Define momentary switch.

Answer 42

a switch that stays on only while it is held pressed

Question 43

# What are some examples of output devices? | (4)

Answer 43

- light emitting diodes (LEDs) - speakers - buzzers - motors

Question 44

# What is a motor?

Answer 44

a component that produces rotary motion when it receives power