Section A: Mechanical Devices

Question 1

What do mechanical devices do

Answer 1

change one form of force into another
input and output motion

Question 2

Name the 4 movements

Answer 2

linear- one dircetion staright line
reciprocating- drone up down/back forth
rotary- movement on/around axis
osciliating- back and forth on curved line

Question 3

What components do levers cosist of

Answer 3

fulcrum- pivot point
effort- input force
load- out force

Question 4

How do you calculate the mechanical advantage

Answer 4

MA= Load/Effort
MA of n
ratio

Question 5

What is a first oder lever (first class)

Answer 5

fulcrum between force and load
Eg pliers

Question 6

What is second order lever (class 2)

Answer 6

fulcrum at one end with effort at opposite end and load anywhere in middle
Eg wheelbarrow

Question 7

What is third order lever (class 3)

Answer 7

fulcrum at one end and effort applied in the middle
Eg tweezers

Question 8

What is a linkage

Answer 8

a mecahanism made by connecting rigid parts. they change the magnitude, direction, transform of a force

Question 9

Explain a push pull linkage

Answer 9

maintains direction of input motion so that output travels in the same direction

Question 10

Explain bell crank linkage

Answer 10

changes direction of input motion through 90*
used to change horizontal motion into vertical motion vice versa

Question 11

What are rotary systems used for

Answer 11

drive mechanisms in equip and machinery
transfer direction of force along different paths and through changes of angle and direction

Question 12

What is a cam

Answer 12

used to change rotary motion into reciprocating motion through use of a follower(movess up/down)

Question 13

Describe a circular/eccentric cam

Answer 13

steady rise and fall

Question 14

Describe a pear cam

Answer 14

rapid rise and long dwell (rest)

Question 15

Describe snail cam

Answer 15

long dwell (rest) and steady rise with sudden drop
only turns in one direction otherwise jam

Question 16

Describe heart shaped cam

Answer 16

slight rise and fall with no rest period

Question 17

What are gears

Answer 17

toothed wheels that mesh to transfer one motion from one part of a machine to another
found in cars, clocks, bicycles, can openers

Question 18

Explain the dirve gear

Answer 18

input turns the driven gear (output)
gears turn opposite directions

Question 19

Explain an idler gear

Answer 19

a smaller gear placed inbetween bigger ones to make sure they go the same way
transfers movement from drive gear to driven so size doesn’t affect speed
driven gear is one after drive gear

Question 20

How do you calculate gear ratio

Answer 20

number of teeth on driven gear/ no teeth on drive gear
for every rotation of drive gear, driven does twice as many- gearing up

Question 21

How to calc velocity ratio

Answer 21

divide drive gear/driven gear

Question 22

What do pulleys do

Answer 22

help lift load
transmit rotary motion and force
not suitable for high torque due to tendancy to slip
belts are made from reinforced rubber or high strength material like kevlar

Question 23

Describe a fixed pulley

Answer 23

wheel with a groove and rope that sits in it
allows to change direction of force needed
lifting easier

Question 24

Describe block and talckle pulley

Answer 24

use of 2/+ pulleys one fixed one moveable to help reduce amount of effort needed
provides mechanical advantage load easier to lift

Question 25

Explain the drive belt loop

Answer 25

loop of flexible rubber
connects 2/+ pulleys together
belt transfers power from pulley to recieving system
Eg in car belt transfers engine power to lternator to recharge battery