Mechanical devices Flashcards
what is linear movement
when something moves in a straight line
rotary movement
where something moves around an axis or pivot
reciprocating movement
a repeated up and down or back and forth motion
oscillating movement
a curved backwards and forwards movement that swings on an axis or pivot point
what are levers
devices that use mechanical advantage to make lifting or applying pressure easier
what is effort
the amount of force applied by the user
what is the fulcrum
where the lever pivots
what is the load
the weight that needs to be moved
what is mechanical advantage
the amount of help you get using a machine in comparison to doing something with just human effort
equation for calculating mechanical advantage
load/effort
what are first class levers
levers with the fulcrum in the middle, between the effort and load
what are second class levers
levers with the load in between the effort and fulcrum
how do first class levers work
If the load is closer to the fulcrum it becomes easier to lift
examples of first class levers
seesaw, crowbar, scissors
When a lever is balanced it has equilibrium
the load is balanced on either side.
examples of second class levers
wheelbarrow, nutcrackers, some bottle openers
how do second class levers work
The closer together the fulcrum and load are, the easier it is to lift the load
what are third class levers
levers with the effort between the fulcrum and the load
examples of third class levers
tweezers or fishing rods
how do third class levers work
If the effort and the fulcrum are further apart, it becomes easier to lift. A third order lever does not have the mechanical advantage
what are linkages
a system of links, can be levers joined together
how do push/ pull linkages work
they use two fixed pivots to make the input and output travel in the same direction, through a link arm
- Changing the placing of the fixed pivots changes the amount of force exerted, while keeping the direction the same
examples of push/pull linkages
a toolbox with drawers opens up
what do bell crank linkages do
change the direction of force through 90
how can you change the output force of a bell crank
by moving the fixed pivot
examples of bell crank linkages and why
used in bicycle brakes, the rider can pull the brakes from the handlebars, which changes direction through the bell crank to make the brake pads touch the wheels.
what is reverse motion/linkage
Reverse motion linkages change the direction of input so that the output goes the opposite way
what is crank and slider
change rotary motion into reciprocating motion, used in car engines
what is a cam mechanism
a shaped part of a pivot which converts reciprocating motion to rotary motion
what is a cam attached to
attached to a crankshaft, which rotates
what is a follower
something that touches the cam and follows the shape, moving up and down
