Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

AQA GCSE - Design and Technology > 1.5 - Mechanical Devices > Flashcards

1.5 - Mechanical Devices Flashcards

1
Q

What are the different types of movement?

A
  • Linear
  • Reciprocating
  • Rotary
  • Oscillating
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Exam Style Question:
Which type of motion best describes the movement of a sewing machine needle?
[1]

A

Reciprocating motion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a lever?

A
  • A lever is a very simple way to gain mechanical advantage (MA), making lifting or moving something much easier.
  • It consists of a rigid bar that pivots or rotates about a fulcrum with a load applied
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What does a typical lever consist of?

A
  • Fulcrum - a pivot point around which a lever turns.
  • Effort - an input force.
  • Load - an output force.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the formula to calculate a lever’s mechanical advantage?

A

MA = Load/Effort

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a first order lever?

A
  • First class levers have the fulcrum between the force and the load.
  • Example: Pliers.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a second order lever?

A
  • Second order levers are most easily remembered as having a wheelbarrow action.
  • The fulcrum is at one end with the effort at the opposite end.
  • The load is anywhere in the middle.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is a third order lever?

A
  • A Class 3 lever has the fulcrum at one end, the load at the opposite end and the effort applied in the middle.
  • Example: Tweezers.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

When a lever is balanced it has ___________ - the load is balanced on either side.

A

equilibrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Define the term ‘Mechanical advantage’.

A

Mechanical advantage is the amount of help you get using a machine in comparison to doing something with just human effort, and it is created by levers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a linkage?

A
  • A linkage is a mechanism made by connecting rigid parts.
  • Linkages can change the magnitude of a force, change the direction of a force or transform it into a totally different motion.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are some different types of linkages?

A
  • Reverse motion
  • Parallel motion / push pull
  • Bell crank
  • Crank and slider
  • Treadle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What ia a ‘reverse motion’ linkage?

A
  • Reverse motion linkages change the direction of input so that the output goes the opposite way.
  • A fixed pivot forces the change in direction. These are often used on foldable clothes horses.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is a ‘parallel motion’ / ‘push pull’ linkage?

A
  • Parallel motion linkages use two fixed pivots to make the input and output travel in the same direction, through a link arm.
  • Changing the placing of the fixed pivots changes the amount of force exerted, while keeping the direction the same.
  • For example, a toolbox with drawers opens up effectively using parallel motion linkages.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a ‘bell crank’ linkage?

A
  • Bell crank linkages change the direction of force through 90°.
  • The amount of output force can be changed by moving the fixed pivot.
  • When used in bicycle brakes, the rider can pull the brakes, which changes direction through the bell crank to make the brake pads touch the wheels.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is a ‘crank and slider’ linkage?

A
  • Crank and slider linkages change rotary motion into reciprocating motion.
  • A fixed pivot is attached to a crank, which turns around and pushes and pulls a slider.
  • When used in a car engine, the ignition of petrol by the spark plugs pushes the slider up, moving the connecting rod and turning the crank.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is a ‘treadle’ linkage?

A
  • Treadle linkages use a rotary input to turn a crank on a fixed pivot.
  • A connecting rod joins two moving pivots to another fixed pivot.
  • This is how a pair of windscreen wipers works on a car, moving backwards and forwards together.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is a rotary system?

A
  • Rotary systems are used to drive mechanisms in equipment and machinery.
  • They transfer the direction of force along different paths and through changes of angle and direction.
  • They include a cam and follower.
19
Q

What is a cam and follower? (Rotary systems)

A
  • A cam is mainly used to change rotary motion into reciprocating motion through the use of a follower.
  • A crank is used to rotate the shaft, which rotates the cam and moves the follower up and down.
20
Q

What are some different types of cams?

A
  • Circular cam
  • Eccentric cam
  • Pear cam
  • Snail cam
  • Heart shaped cam
21
Q

Describe the reciprocating motion produced by circular / eccentric cams?

A
  • Steady rise and fall.
22
Q

Describe the reciprocating motion produced by pear cams?

A
  • Rapid rise and fall followed by long dwell (rest).
23
Q

Describe the reciprocating motion produced by snail cams?

A
  • Long dwell followed by steady rise and sudden drop.
  • This can only turn in one direction, otherwise the mechanism would jam.
24
Q

Describe the reciprocating motion produced by heart shaped cams?

A
  • Slight rise and fall with no dwell period.
25
Q

Exam Style Question:
A child’s toy crocodile has a mouth that slowly opens and snaps shut again when a handle is turned.

Suggest the most suitable cam to be used to create this mechanism.
[1]

A

A snail cam.

26
Q

What is a gear?

A
  • Gears are toothed wheels, that mesh to transfer motion from one part of a machine to another.
  • Gears are found in many things from cars and bicycles, to clocks and can openers.
27
Q

What are the three main types of followers?

A
  • Flat
  • Point or knife
  • Roller
28
Q

What are the qualities of a flat follower?

A
  • Flat followers have a flat bottom that sits on the cam.
  • These cope well under load but aren’t very accurate and have a lot of friction.
29
Q

What are the qualities of a point/knife follower?

A
  • Point or knife followers have a narrow point that sits on the cam.
  • These are very accurate and low friction but are quick to wear away the pointed edge.
30
Q

What are the qualities of a roller follower?

A
  • Roller followers have a roller such as a ball bearing attached to the bottom of the following.
  • These are accurate, low on friction and can withstand load, but are more costly to produce.
31
Q

What is a gear?

A
  • Gears are toothed wheels, that mesh to transfer motion from one part of a machine to another.
  • Gears are found in many things from cars and bicycles, to clocks and can openers.
32
Q

What is a gear train?

A
  • Gear trains are when two or more gears are joined together.
  • A gear train transmits rotary motion and torque.
  • Different sized gears connect to increase or decrease the speed of rotation.
33
Q

What is torque?

A

Torque is a force that causes rotation.

34
Q

What is a ‘drive gear’?

A
  • The drive gear (input) turns the driven gear (output).
  • The gears turn in opposite directions.
35
Q

What is an ‘idler gear’?

A
  • An idler gear is used to change the direction of rotation so that the driven gear turns in the same direction as the drive gear.
  • It transfers movement from the drive gear to the driven, so size does not affect speed.
36
Q

How do you calculate gear ratio? (Gear trains)

A

Number of teeth on driven gear : number of teeth on driver gear

Or

Number of teeth on driven gear / number of teeth on driver gear

37
Q

How do you calculate velocity ratio? (Gear trains)

A

Velocity ratio = drive gear / driven gear

38
Q

What are pulley systems?

A
  • Pulleys can help to lift a load providing a mechanical advantage.
  • In machines, pulleys transmit rotary motion and force from the drive shaft (input) to the driven shaft (output).
  • Pulleys are not ideal for transmitting high torque due to their tendency for the belt to slip.
  • Belts are often made of reinforced rubber or high strength materials such as Kevlar.
39
Q

What are the two types of pulley systems?

A
  • Fixed pulley
    (no mechanical advantage)
  • Block and tackle pulley
    (has mechanical advantage)
40
Q

What is a ‘fixed pulley’?

A
  • A fixed pulley uses a wheel with a groove in it and a rope that sits in the groove.
  • It allows you to change the direction of the force needed, which makes lifting easier, but the weight will feel the same (no mechanical advantage).
41
Q

What is a ‘block and tackle pulley’?

A
  • A block and tackle pulley uses two or more pulleys, one fixed and one moveable, to help reduce the amount of effort needed to lift a load.
  • It provides a mechanical advantage making a load easier to lift.
42
Q

How do you calculate the effort needed to raise a load using a pulley system?

A

Effort = load / number of pulleys

43
Q

How are belts used in pulley systems?

A
  • A drive belt (loop of flexible rubber) connects two or more pulleys together.
  • The belt transfers power from the pulley to the receiving system.
  • In the instance of a car, a belt transfers engine power to the alternator to recharge the battery.

AQA GCSE - Design and Technology (25 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions