work and machines test part 1,3,4

work

when the force causes an object to move in the direction of the force

power

how fast work is being done

in science power is the rate at which energy is being transferred

force

a push or pull on an object

machine

A device that makes work easier

work input

work done on a the machine called input force ex: opening and closing scissors (wi)

work output

work done by the machine called output force ex: scissors cutting paper (Wo)

mechanical advantage

measure of the force achieved by using a machine

mechanical efficiency

a machine has a higher mechanical efficiency if it takes a smaller work input to get a greater work output

lever

A bar that pivots at a fixed point called a fulcrum

class one lever

the fulcrum is between the input force and the load

class 2 lever

the load is between the the fulcrum and the input force (effort) ex: wheelbarrow

class 3 lever

the input force is between the fulcrum and the load (effort is in the middle) ex: tweezers

Pulley

a grooved wheel that holds a rope or cable a load is on one end and the input force is on the other

wheel and axel

2 circular objects of different sizes ( larger is wheel, smaller is axel)

inclined plane

a flat, sloped surface ex: ramp

wedge

a pair of incline planes that move ex: knife

screw

An inclined plane wrapped in a spiral around a cylinder

compound machine

a machine made of more than one simple machine ex: wheel barrow