STUFF 3

Question 1

What are mechanisms used for?

Answer 1

to make a force bigger or smaller

Question 2

What are the 4 types of movement?

Answer 2

linear
reciprocating
rotary
oscillating

Question 3

What is the difference between reciprocating and oscillating?

Answer 3

reciprocating is linear motion
oscillating is curved motion

Question 4

What are 4 examples of simple mechanisms?

Answer 4

screw
wheel and axle
wedge
lever
pulley
wheelbarrow

Question 5

How do you work out mechanical advantage?

Answer 5

load/effort

Question 6

What is the difference between the driver gear and the driven gear?

Answer 6

the driver is the input gear
the driven is the output gear

Question 7

What are gear trains?

Answer 7

consist of multiple interlocking gears that transmit torque and rotary motion

Question 8

What is torque?

Answer 8

the turning force that causes rotation

Question 9

How can you change the direction of the output gear?

Answer 9

using an idler gear
it is added to make the direction of rotation the same as that of the input gear

Question 10

How do you change the speed of gears?

Answer 10

to make the output speed faster, the input gear must be larger than the output gear
to make the output smaller, the input gear must be smaller than the output gear

Question 11

How do you calculate gear ratios?

Answer 11

the larger gear is always 1
the smaller gear is calculated by dividing the number of teeth on the larger gear by the number of teeth on the smaller gear

Question 12

What do cam mechanisms do?

Answer 12

used to convert rotary motion into reciprocal motion and consist of a cam and follower

Question 13

What is the structure of a cam mechanism?

Answer 13

a cam is a specifically shaped piece of material attached to a rotating shaft
the follower rests on the cam and rises and falls as the cam rotates

Question 14

What other things can a cam mechanism include and what do they do?

Answer 14

slide - prevent the follower from slipping
crank - (handle) to manually rotate the camshaft
wheel follower - to reduce friction between the cam and follower

Question 15

What is a wheel follower?

Answer 15

a wheel attached to the bottom of the follower

Question 16

What are the 4 types of cams?

Answer 16

eccentric
pear-shaped
snail
heart-shaped

Question 17

What does an eccentric cam do?

Answer 17

the rotating shaft is positioned off-centre, causing the follower to steadily rise and fall

Question 18

What does a snail cam do?

Answer 18

the follower gradually rises and then suddenly drops
it can only rotate in one direction

Question 19

What does the pear-shaped cam do?

Answer 19

the follower remains stationary for half a turn, it then rises as the point approaches for a quarter turn before falling for the last quarter

Question 20

What does a heart shaped cam do?

Answer 20

the follower rises and falls with no stationary period
it is said to have a constant velocity

Question 21

Why are pulleys used?

Answer 21

a simple pully does not provide mechanical advantage but can make things easier to lift by changing the direction of the force
using two or more pulleys together can provide mechanical advantage

Question 22

What are belt and pulley systems and what do they do?

Answer 22

multiple pulleys are connected by a belt to transfer rotary motion and force from the driver pulley to the driven pulley

Question 23

Where are belt and pulley systems used?

Answer 23

car engines and washing machines

Question 24

What are belts made of in belt and pulley systems?

Answer 24

rubber to reduce slippage as they need to remain taut

Question 25

How can you change the direction of the driven pulley?

Answer 25

by crossing the belts

Question 26

What does the velocity ratio show?

Answer 26

the ratio of rotations of each pulley

Question 27

What does differing pulley sizes do?

Answer 27

when driver pulley is larger, driven pulley will rotate faster but the torque will be less when driver pulley is smaller, driven pulley will rotate slower but torque will be greater

Question 28

How is the velocity ratio calculated?

Answer 28

diameter of driver pulley : diameter of driven pulley

Question 29

What is a block and tackle system?

Answer 29

a way of using multiple pulleys together to provide mechanical advantage

Question 30

What is a lever?

Answer 30

a mechanical device used to transmit and transform the effects of forces

Question 31

What are the 3 parts to a lever?

Answer 31

effort fulcrum load

Question 32

How do you remember the order of the classes of levers?

Answer 32

FRE first order: fulcrum in the middle second order: resistance in the middle third order: effort in the middle

Question 33

What are 2 examples of each type of lever class?

Answer 33

1st: scissors, seesaw 2nd: bottle opener, wheelbarrow 3rd: tweezers, the human arm

Question 34

What are linkages?

Answer 34

lever joined together transmit force and motion at a distance from the initial input

Question 35

What are the 3 types of linkages?

Answer 35

push/pull bell crank changing magnitude force

Question 36

What do push/pull linkages do?

Answer 36

create an identical parallel motion at the output

Question 37

What do bell crank linkages do?

Answer 37

changes the direction of the motion by 90 degrees

Question 38

How do changing magnitude of force linkages work?

Answer 38

if the fixed point is closer to output than the output force will be greater if fixed point is closer to input than the output force will be smaller if fixed point is equal distance, input force = output force

Question 39

Describe a rack and pinion.

Answer 39

converts rotary motion into linear motion consists of a toothed bar called a rack and a circular gear called a pinion