Simple Machines Flashcards
Equation to find work
work= force x distance
- if the distance you move an object increases, the force required decreases
Mass
- amount of matter an object contains
- mass of an object cannot change unless a part of the object is lost or another part is added
- measured in kg
Effort
the force you put in to move or change the position of an object
load
the weight of the object being lifted or carried
Ist class lever
LiFE
- direction changer
- force multiplier
2nd class lever
ELF
-Force multiplier
3rd class lever
LEaF
-speed multiplier
Force multipliers
- change small applied force into larger resultant force
Example: tweezer, crowbar
Speed multiplier
Slow speed into faster resultant speed
Example: Car wheels, egg beaters
Direction changers
-machines that change the direction in which a force acts
Example: blinds
Can a machine be a speed+force multiplier?
No machine is both a speed and a force multiplier because then you’d get more work out than you put in
Work
- energy required to move an object over a certain distance
- measured in joules (J)
relationship equation of work input and work output
work input=work output (approximately)
(Fe x De)=(Fl x Dl)
Less useable energy comes out that what was put in because energy can be lost due to heat loss, friction, etc.
Efficiency of a machine (as a %)
energy output/ energy input x 100
MA (Levers)
dE/dL
fL/fE
Speed multiplier or force multiplier?
Speed multiplier = mechanical advantage 1
Gears
Wheels with teeth
When one gear turns, the one it interlocks with also turns but in the opposite direction
Driver or driven?
Driver gear- gear turned first
Driven gear- turned by driver gear
Gears- force multiplier or speed multiplier?
force- when effort is applied to smaller gear, the larger gear will turn more slowly but with greater force
speed- when effort is applied to larger gear, smaller gear will turn faster.
idler gear
used in between driver and driven gear to make them turn in the same direction
Bevel gear
positioned at right angles to one another to change the plane of rotation
Rack and pinion
made up of a row of teeth -rack- and a gear wheel that rolls on top of this -pinion- which converts rotational movement into linear movement.
MA of gears
no. teeth on driven/ no. teeth on driver
gear ratios
no. teeth on driver/ no. teeth on driven
Chain drives in a bicycle
- reduce slipping by having toothed gears
- the gear used in a bicycle is called a rear sprocket wheel.
- the pedal is attached to the chain drive which is then attached to the rear sprocket wheel
High gear
- Faster speed
- Flat roads
- rear sprocket wheel is smaller, chain wheel is larger
Low gear
-Slower speed
-greater force
-uphill
rear sprocket is larger, chain wheel is smaller
What is a pulley?
- A pulley is a wheel with a groove around it which can fit a rope.
- Pulley is a form of lever, with its axle as the pivot/fulcrum
Simple pulley system
- pulley system that lifts a weight up when another end of the rope is pulled down
- direction changer
Compound pulley system
- when there are two or more pulleys to lift the same load.
- You have to pull the rope twice as far
- force multiplier.
Pulleys: the more times the rope supports the load…
the easier it is to lift (the more axles being used)
MA of pulleys
-calculated by counting the number of ropes supporting the load (rope where effort is applied is not counted.
Inclined plane
- flat surface that’s higher on one end
- they produce a ma by increasing the distance through which a force moves.
- as the length of the slope increases and the height decreases, the effort required decreases.
MA of inclined plane
length of slope/ height of inclined plane
Screw
inclined plane wound around a central cylinder
Eg. drills+jar lids
MA of screw
circumference/ pitch
pitch= 1/ no. of turns per inch
Wedges
2 inclined planes joined back-to-back
used to split things
MA of wedges
length of either slope/ thickness of big end
MA of wheels+axles
radius of wheel/ radius of axle
Speed multiplier- wheel and axle
When the input force is on wheel, output on axle
Force multiplier- wheel and axle
input on axle, output on wheel
