Term 3 Topic 3 Unit 1 Mechanical systems

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Term 3 Topic 3 Unit 1: Mechanical systems & control (machines, levers & their

Term 3 Topic 3 Unit 1: Mechanical systems & control (machines, levers & their functions)

MACHINES ARE ABLE TO: -Increase amount of force to move a bigger load -This

MACHINES ARE ABLE TO: -Increase amount of force to move a bigger load -This machine = FORCE MULTIPLIER -Increase distance that object moves -This machine = DISTANCE MULTIPLIER

FORMULA FOR AMOUNT OF WORK DONE: Work = Force x distance W=Fxd J=Nxm Amount

FORMULA FOR AMOUNT OF WORK DONE: Work = Force x distance W=Fxd J=Nxm Amount of work done (W) = measured in Joules (J) Force (F) measured in Newtons (N) Distance (d) measured in metres (m)

EXAMPLE: -Wheelbarrow is pushed 50 m -Using a force of 20 N -How much

EXAMPLE: -Wheelbarrow is pushed 50 m -Using a force of 20 N -How much work has been done? Let’s see who can find this answer first!!! =D

EXAMPLE ANSWER: Wheelbarrow is pushed 50 m = distance (d) in m Using a

EXAMPLE ANSWER: Wheelbarrow is pushed 50 m = distance (d) in m Using a force of 20 N = force (F) in N How much work has been done? = Work (W) in J Therefore W=Fxd W = 20 N x 50 m W = 100 Nm or 100 J

CLASS ACTIVITY: -Car is moved 85 m -Using a force of 120 N -How

CLASS ACTIVITY: -Car is moved 85 m -Using a force of 120 N -How much work has been done? Let’s see who can find this answer first!!! =D

CLASS ACTIVITY: 1. What is the formula used for WORK DONE? 2. How much

CLASS ACTIVITY: 1. What is the formula used for WORK DONE? 2. How much work did Jo do to push his toy car 6. 4 m with a force of 15 N? 3. If Jo needed 45 J to push his car 8 m, then how much force did he need? 4. If Jo used 56 N of force & 62 J of work, then how far did he push his toycar?

MECHANISMS: -DEFINITION: -Different parts working together to perform a specific task -They are the

MECHANISMS: -DEFINITION: -Different parts working together to perform a specific task -They are the parts that make work easier -Convert INPUT force to an OUTPUT force

A JACK used on a CAR: -Turn the screw of jack = INPUT force

A JACK used on a CAR: -Turn the screw of jack = INPUT force -Jack raised higher = PROCESS -Car lifted up = OUTPUT force -Is the jack a force multiplier or a distance multiplier? ? ? = FORCE MULTIPLIER (makes it easier to lift car)

MECHANICAL SYSTEM: -DEFINITION: -When a machine uses a mechanical appliance (like the screw of

MECHANICAL SYSTEM: -DEFINITION: -When a machine uses a mechanical appliance (like the screw of the jack) to provide force for movement -OTHER MACHINES THAT USE OTHER SYSTEMS: -Electrical systems (work with electricity) -Hydraulic systems (work with liquid under pressure) -Pneumatic systems (work with air under pressure)

A D CLASS ACTIVITY B Label the following as either: Hydraulic E Or C

A D CLASS ACTIVITY B Label the following as either: Hydraulic E Or C Pneumatic Or Electrical F

LEVERS: -DEFINITION: -Bar free to turn about a fixed point or pivoting point (FULCRUM)

LEVERS: -DEFINITION: -Bar free to turn about a fixed point or pivoting point (FULCRUM) -Are simple machines -3 classes: -A) first class levers -B) second class levers -C) third class levers

SINGLE-FIRST CLASS LEVERS: -DEFINITION: -When fulcrum (F) lies between Load (L) & Effort (E)

SINGLE-FIRST CLASS LEVERS: -DEFINITION: -When fulcrum (F) lies between Load (L) & Effort (E) -Mechanical advantage (M. A. ): -Depends on position of fulcrum -If F closer to L than E, then will be M. A.

LINKED FIRST-CLASS LEVERS: -DEFINITION: -Some cases 2 levers linked together at fulcrum e. g.

LINKED FIRST-CLASS LEVERS: -DEFINITION: -Some cases 2 levers linked together at fulcrum e. g. pair of scissors -Normal paper scissors blades equal in length to handle = NO M. A -Pruning scissors long handle & short, strong blades = M. A. greater than 1 -Express as MA > 1 -i. e. less force to get work done

SINGLE-SECOND CLASS LEVERS: -DEFINITION: -When Load (L) is between Fulcrum (F) & Effort (E)

SINGLE-SECOND CLASS LEVERS: -DEFINITION: -When Load (L) is between Fulcrum (F) & Effort (E) -Always gives some kind of M. A.

SINGLE-SECOND CLASS LEVERS: -IMPORTANT: -If given MA > 1 -Means output force is bigger

SINGLE-SECOND CLASS LEVERS: -IMPORTANT: -If given MA > 1 -Means output force is bigger (>) than input force -i. e. when person presses lever they use less force to get the work done

LINKED SINGLE-SECOND CLASS LEVERS: -DEFINITION: -Formed when 2 nd class levers joined at fulcrum

LINKED SINGLE-SECOND CLASS LEVERS: -DEFINITION: -Formed when 2 nd class levers joined at fulcrum -E. g. office punch -Gives M. A. > 1 (what does this mean? ) -Why? ? ? -F fixed at a point where operator needs less Effort to perform the task

SINGLE-THIRD CLASS LEVERS: -DEFINITION: -Effort (E) is between Fulcrum (F) & Load (L) -Never

SINGLE-THIRD CLASS LEVERS: -DEFINITION: -Effort (E) is between Fulcrum (F) & Load (L) -Never gives Mechanical Advantage (M. A. < 1) -i. e. requires more effort than Weight of Load -E. g. ’s: -Fishing rod -Light duty stapler -Pair of tweezers

SINGLE-THIRD CLASS LEVERS: -IMPORTANT: -Often small movement at 1 end will produce a larger

SINGLE-THIRD CLASS LEVERS: -IMPORTANT: -Often small movement at 1 end will produce a larger movement at the other end -E. g. fishing rod

LINKED THIRD-CLASS LEVERS: -DEFINITION: -Formed when 3 rd class levers joined at fulcrum -E.

LINKED THIRD-CLASS LEVERS: -DEFINITION: -Formed when 3 rd class levers joined at fulcrum -E. g. office stapler -M. A. < 1 -Why? ? ? -Effort too close to fulcrum to give a greater M. A.

CLASS ACTIVITY: Identify the 3 different classes of levers (Let’s do this together) –

CLASS ACTIVITY: Identify the 3 different classes of levers (Let’s do this together) – first draw the 3 lever classes A B C

GEAR SYSTEMS

GEAR SYSTEMS

-FORCE DEFINITION: -Make things move -TORQUE DEFINITION: -Force applied that causes an object to

-FORCE DEFINITION: -Make things move -TORQUE DEFINITION: -Force applied that causes an object to rotate around an axis -COUNTER ROTATION: -2 wheels rotating in opposition directions -i. e. a gear consist of 2 such wheels

-GEARS: -Transfer rotating movement -DIFFERENCE BETWEEN GEAR & PULLEY? ? ? -Gears have teeth

-GEARS: -Transfer rotating movement -DIFFERENCE BETWEEN GEAR & PULLEY? ? ? -Gears have teeth which directly engage with each other & prevent 2 wheels from slipping

SPUR GEARS or straight cut gears: -DEFINITION: -Consist of a disk with teeth projecting

SPUR GEARS or straight cut gears: -DEFINITION: -Consist of a disk with teeth projecting from inside outward -Edge of each tooth is straight -When spur gears mesh / join smaller gear = PINION Bigger gear = WHEEL

SPUR GEARS or straight cut gears: -1 gear turned by motor = DRIVER gear

SPUR GEARS or straight cut gears: -1 gear turned by motor = DRIVER gear -Driver gear meshes with other gear -Second gear = DRIVEN gear -Often spur gears are unequal sizes -This means different numbers of teeth for each -M. A. now produced

SPUR GEARS or straight cut gears: -Smaller gear rotates faster vs bigger gear -BUT

SPUR GEARS or straight cut gears: -Smaller gear rotates faster vs bigger gear -BUT -Bigger gears TORQUE is greater (although turns slower)

HOW TO CALCULATE GEAR RATIO aka VELOCITY RATIO • Gear ratio = number of

HOW TO CALCULATE GEAR RATIO aka VELOCITY RATIO • Gear ratio = number of teeth of the driven gear --------------------number of teeth of the driven gear • Velocity ratio is also used for gear ratio

CLASS ACTIVITY: Lets work out the Velocity ratio of the spur gear below (let’s

CLASS ACTIVITY: Lets work out the Velocity ratio of the spur gear below (let’s see who can do it first =D) Don’t forget your ratio value & statement

BICYCLE (spur gear) EXAMPLE: -Pedal gear = front gear DRIVER GEAR -Differs in size

BICYCLE (spur gear) EXAMPLE: -Pedal gear = front gear DRIVER GEAR -Differs in size to back gear DRIVEN GEAR -Changing Velocity ratio forces cyclist to use more force on driver gear

TWO SPUR GEARS CONNECTED VIA AN IDLER GEAR: -GEAR TRAIN DEF: -Made up of

TWO SPUR GEARS CONNECTED VIA AN IDLER GEAR: -GEAR TRAIN DEF: -Made up of 2 or more gears -1 st gear may rotate clockwise -2 nd gear may rotate anti-clockwise -3 rd gear would rotate in direction of 1 st gear -Often gears in Gear train are different sizes & will rotate at different speeds

TWO SPUR GEARS CONNECTED VIA AN IDLER GEAR: -IDLER GEAR: -Forces 2 outer gears

TWO SPUR GEARS CONNECTED VIA AN IDLER GEAR: -IDLER GEAR: -Forces 2 outer gears to turn in same direction -Called SYNCHRONISATION -NOTE: -Could also make size of shape the size to have them turn at the same velocity

SUITABLE MATERIALS: -IDLER GEAR FUNCTION: -Influence rotation of 2 important gears -Therefore Idler gear

SUITABLE MATERIALS: -IDLER GEAR FUNCTION: -Influence rotation of 2 important gears -Therefore Idler gear much smaller than other 2 gears & found between driven & driver gear -Bears all force & wear of other 2 gears -MUST BE: strong, hard material that wont break / affect speed & functioning of the other 2 gears

TWO BEVEL GEARS: Find pics / videos of working bevel gear -When linked together

TWO BEVEL GEARS: Find pics / videos of working bevel gear -When linked together transfer axis of rotation through 90° -i. e. change direction of drive through 90° -Have cone-shaped teeth cut at 45° angle -E. g. hand drill mechanism

Term 3 Topic 3 Unit 2: Mechanical advantage calculations

Term 3 Topic 3 Unit 2: Mechanical advantage calculations

RATIOS: Find videos of ratios -DEFINITION: -Describes a relationship between 2 things in numbers

RATIOS: Find videos of ratios -DEFINITION: -Describes a relationship between 2 things in numbers -i. e. the relative sizes of 2 or more things -What does the ratio of 4: 3 mean? ? -E. g. there could be 4 oranges for every 3 apples -If there are now 8 oranges -Then 4 oranges x 2 = 8 oranges -So 3 apples x 2 = 6 apples What we do on the 1 side we do on the other side

LEVERS & MECHANICAL ADVANTAGE: -Levers give us mechanical advantage -This means: -Levers help us

LEVERS & MECHANICAL ADVANTAGE: -Levers give us mechanical advantage -This means: -Levers help us lift heavy weights with little effort

SPEED RATIO: Speed ratio = distance moved by force (effort) --------------distance moved by load

SPEED RATIO: Speed ratio = distance moved by force (effort) --------------distance moved by load

SPEED RATIO EXAMPLE: Calculate the speed ratio of the mechanism if the distance moved

SPEED RATIO EXAMPLE: Calculate the speed ratio of the mechanism if the distance moved by the force was 20 & the distance moved by the load was 80 Let’s see who can do this first!! =D

SPEED RATIO EXAMPLE ANSWER: Speed ratio = ? ? ? Our formula: speed ratio

SPEED RATIO EXAMPLE ANSWER: Speed ratio = ? ? ? Our formula: speed ratio = distance moved by the force ----------------distance moved by the load Speed ratio = 20 = 1 ------ 80 4 = 1: 4 Means: force had a MA over the load i. e. the force moved 1 x for every 4 x that the load moved

SPEED RATIO EXAMPLE: What does this really mean? ? ? Find pic of eraser

SPEED RATIO EXAMPLE: What does this really mean? ? ? Find pic of eraser on a lever system Every 1 time the forefinger moved (i. e. its distance moved), the eraser moved 4 times Therefore the lever is a DISTANCE MULTIPLIER!

MECHANICAL ADVANTAGE OF A MECHANISM: MA = load ----force Load & force are both

MECHANICAL ADVANTAGE OF A MECHANISM: MA = load ----force Load & force are both measured in Newtons (N) Newtons = unit of force Find videos of newtons

MECHANICAL ADVANTAGE OF A MECHANISM EXAMPLE: Calculate the MA of a mechanism with a

MECHANICAL ADVANTAGE OF A MECHANISM EXAMPLE: Calculate the MA of a mechanism with a load of 40 and a force of 70. Let’s see who can do this first!! =D Find pics of load & effort

MECHANICAL ADVANTAGE OF A MECHANISM EXAMPLE ANSWER: Calculate the MA of a mechanism with

MECHANICAL ADVANTAGE OF A MECHANISM EXAMPLE ANSWER: Calculate the MA of a mechanism with a load of 40 and a force of 70. MA = ? ? ? MA = Load Find pic of thinking caps = 40 = 1 ------- Force 70 1. 75

1 NEWTON: A force that is 1 N strong Find pics of slab of

1 NEWTON: A force that is 1 N strong Find pics of slab of chocolate = the weight of 100 g mass e. g. you experience 1 N of force when you hold a 100 g slab of chocolate So how many Newtons would you experience with a 650 g slab of chocolate? ? ? = 6. 5 N (i. e. 650 g / 100 g = 6. 5 N)

M. A. CALCULATIONS FOR GEARS USING RATIOS: - When we mesh 2 gears together,

M. A. CALCULATIONS FOR GEARS USING RATIOS: - When we mesh 2 gears together, they act similar to levers - Each end of a gear’s tooth = similar to the end of a lever with a fulcrum at the gear’s centre - Longer lever A is greater the force applied to the shaft of the driven gear Find pics & video of MA for gears using ratios

- SHAFT DEFINITION: -Drive shaft that transfers torgue (i. e. turning motion of a

- SHAFT DEFINITION: -Drive shaft that transfers torgue (i. e. turning motion of a gear around a fixed point) -Gears DO NOT ONLY increase speed & change direction -BUT they also MULTIPLY TURNING FORCES

M. A. CALCULATIONS USING TOOTH RATIOS FOR GEARS: Gear ratio (velocity ratio) = number

M. A. CALCULATIONS USING TOOTH RATIOS FOR GEARS: Gear ratio (velocity ratio) = number of teeth of driven ---------------number of teeth of driver Calculate the gear ratio if the driven gear has 60 teeth & the driver gear has 15 teeth Let’s see who can do this first!! =D

M. A. CALCULATIONS USING TOOTH RATIOS FOR GEARS ANSWER: Gear ratio (velocity ratio) =

M. A. CALCULATIONS USING TOOTH RATIOS FOR GEARS ANSWER: Gear ratio (velocity ratio) = number of teeth of driven ---------------number of teeth of driver Gear ratio = 60 = 4 ------ 15 1 = 4: 1 This means that the MA ratio is 4: 1 So the driven gear turns 4 x more than the driver gear

CALCULATING GEAR WHEEL DIAMETER FOR GEARS: A gear’s most NB feature is that gears

CALCULATING GEAR WHEEL DIAMETER FOR GEARS: A gear’s most NB feature is that gears of unequal sizes (diameters) can be combined to produce a MA -A different arrangement of different gear sizes = a ‘gear ratio’ -& the number of teeth / gear diameter is used as the units Find pics & video of gear trains & MA for gear combinations -Let’s determine the MA of a particular gear combination

CALCULATING GEAR WHEEL DIAMETER FOR GEARS: MA = output force ------input force Calculate the

CALCULATING GEAR WHEEL DIAMETER FOR GEARS: MA = output force ------input force Calculate the MA if the output force is 60 N & the input force was 40 N Answer: MA = 60 N = 1 ------- 40 N 1. 5 N = 1 N : 1. 5 N

CALCULATION USING VELOCITY RATIOS (i. e. gear ratios): Velocity Ratio = Driver gear (the

CALCULATION USING VELOCITY RATIOS (i. e. gear ratios): Velocity Ratio = Driver gear (the one connected to the power) ------Driven gear We use the number of teeth of the gears to calculate VR (velocity ratio)

CALCULATION USING VELOCITY RATIOS (i. e. gear ratios): Then: We want to calculate the

CALCULATION USING VELOCITY RATIOS (i. e. gear ratios): Then: We want to calculate the speed of the driven gear So: Our VR = 12 = 1 = 0. 5 --- 24 2 If driven speed = 1 000 rpm Then final speed = 1 000 rpm x VR (i. e. 0. 5) = 500 rpm

CALCULATION USING VELOCITY RATIOS EXTRA EXAMPLE: Let’s see if you can do this one

CALCULATION USING VELOCITY RATIOS EXTRA EXAMPLE: Let’s see if you can do this one by yourself =D The driver gear has 60 teeth The driven gear has 30 teeth What is the VR? If the driven speed is 1 000 rpm? What is the final speed of the driven gear?

CALCULATION USING VELOCITY RATIOS EXTRA EXAMPLE ANSWER: VR = driver = 60 = 2

CALCULATION USING VELOCITY RATIOS EXTRA EXAMPLE ANSWER: VR = driver = 60 = 2 ------- --- driven 30 1 = 2 0 r 2 , 0 Driven speed = 1 000 rpm So final driven speed = 1 000 rpm x VR = 1 000 rpm x 2, 0 = 2 000 rpm

Term 3 Topic 3 Unit 3: COMMUNICATION & DESIGN SKILLS

Term 3 Topic 3 Unit 3: COMMUNICATION & DESIGN SKILLS

REPRESENTING GEAR SYSTEMS GRAPHICALLY: GRAPHICALLY DEFINITION: Show a design through drawings, sketches, plans &

REPRESENTING GEAR SYSTEMS GRAPHICALLY: GRAPHICALLY DEFINITION: Show a design through drawings, sketches, plans & diagrams COUNTER ROTATING Turning in opposite directions How would we graphically represent this? ? ?

Find pics of gears graphically represented

Find pics of gears graphically represented

REPRESENTING GEAR SYSTEMS GRAPHICALLY: IDLER GEARS INBETWEEN SPUR GEARS Let’s graphically represent this Find

REPRESENTING GEAR SYSTEMS GRAPHICALLY: IDLER GEARS INBETWEEN SPUR GEARS Let’s graphically represent this Find pics of spur gear with idler gear graphically represented with rotation directions

REPRESENTING GEAR SYSTEMS GRAPHICALLY: How would we represent the DRIVEN GEAR turning faster &

REPRESENTING GEAR SYSTEMS GRAPHICALLY: How would we represent the DRIVEN GEAR turning faster & turning slower? ? Find pics of driven gear turning faster & slower graphically (look for driven gear being bigger & smaller than driver gear)

IMPORTANT TERMS: OUTPUT VELOCITY DEFINITION: The rate of speed of the output from an

IMPORTANT TERMS: OUTPUT VELOCITY DEFINITION: The rate of speed of the output from an electronic device FORCE MULTIPLIER DEFINITION: Something that makes a given force more effective than that same force would be without it Find pics output velocity & force multipliers