Unit 3 - Mechanics Flashcards
Outline Newton’s first law
when the resultant force is 0N, it will maintain velocity, including if it is stationary
Outline Newton’s second law
F=ma
Outline Newton’s third law
every force has an equal and opposite reactive force
Outline the term brittle in terms of material properties
doesn’t plastically deform before failure
Outline the term ductile in terms of material properties
ability of an object to deform without breaking (usually along its length)
Outline the term tough in terms of material properties
ability of an object to resist failure when receiving a blow to shock
Outline the term hard in terms of material properties
ability for a material to resist abrasion (scratching from the environment)
Outline the term malleable in terms of material properties
ability to be reshaped (deform) without failing
Outline the term stiffness in terms of material properties
the amount of stress applied for 1 unit of strain - Youngs modulus
Outline the term factor of safety and its equation
FoS = allowable stress / ultimate stress
also known as potential failure limit
FoS is the largest value of stress a material can withstand
Outline the equation for the centre of mass away from the edge of a semi-circle
4r / 3pi
Outline the three types of levers and how to remember their order
Class 1 - Fulcrum
Class 2 - Load
Class 3 - Effort
Outline the equation for mechanical advantage (MA) for Levers
load / effort
Fout / Fin
a / b
1 / VR
Outline the equation for velocity ratio (VR) for Levers
effort / load
Fin / Fout
b / a
1 / MA
Outline the position of A and B in any lever system
A is between the Fulcrum and Effort
B is between the Fulcrum and Load
Name the 8 types of gears
Spur
Compound Spur
Idler
Chain and Gear
Bevel
Rack and pinion
Worm gears/wheels
Helical gears
Outline Spur gears
Most common gear used
Noisy
Cheap to manufacture
Round with equally sized teeth
Outline Compound Spur gears
used to alter direction and speed
gears will make the next one move in the opposite direction
small to big gears - slower
big to small gears - faster
Outline Idler gears
uses spur gears with one extra gear in the middle
used to make the first and last gears move in the same direction
can be used just to fill the space
Outline Chain and Gear system
two chains apart from each other, connected via a chain with teeth
used to drive a chain or pulley
gears move in the same direction
Outline Bevel gears
changes the axis of the gears by 90 degrees
changes direction
Outline Rack and pinion gears
pinion (spur) gear is used to move a rack
used in motor vehicles to change direction when turning wheel
Outline worm gears/wheels
long rod (worm) turned to move wheel (spur)
only goes one direction as there is too much friction to go the other way
teeth are slanted
slows stuff down fast
if there are n shafts (teeth) on wheel, it take n turns of the worm for 1 turn of the wheel
Outline Helical gears
double helix stops a sideways force being exerted in a single helix.
Outline the equation for mechanical advantage (MA) in gears
number of teeth on output
/
number of teeth on input
1 / VR
Outline the equation for velocity ratio (VR) in gears
number of teeth on input
/
number of teeth on output
1 / MA
Outline the equation for mechanical advantage (MA) in a pulley system
diameter of output
/
diameter of input
1 / VR
Outline the equation for velocity ratio (VR) in a pulley system
diameter of input
/
diameter of output
1 / MA
Outline the three types of pulleys
Flat
V-belts
Toothed
Outline a flat pulley
flat rubber band connecting two smooth gears
cheap to manufacture
can slide off easily
max speed 51m/s
can warp due to heat
Outline a V-belt pulley
v shaped belt slotted into a pulley
doesn’t slip sideways
faster than a flat belt
can still slip along
more expensive than a flat belt
Outline a toothed pulley
toothed chain connecting two gears
chain can be metal or rubber
max speed 82m/s
doesn’t slip in any direction
expensive
