Machines & Mechanical Systems

What is a machine? A device with moving parts that work together to accomplish a task a device that makes work easier by changing the size or direction of an applied force (input force) Machines are designed to do something useful Machines DO NOT change the amount of WORK accomplished!

Same Work Someone loading a truck will perform the same work lifting the boxes directly into the truck as a person that walks up a ramp carry the same boxes. The end result is the truck is loaded.

Simple Machine an unpowered mechanical device i.e. lever, wheel and axle, the block and tackle (pulley system), the gear, and the ramp

Input vs. Output The input includes everything you do to make the machine work The output is what the machine does for you

Mechanical Advantage is the ratio of output force to input force

Mechanical Advantage If the mechanical advantage is more than one, the output force is bigger than the input force A mechanical advantage smaller than one means the input force is bigger than the output force

fulcrum Output arm Input arm Levers are useful because we can arrange the fulcrum and the lengths of the input and output arms to make almost any mechanical advantage we need.

Mechanical Advantage MA > 1 if di > do MA = 1 if di = do of MA > 1 if di > do MA = 1 if di = do MA < 1 if di < do MA > 1 (di > do) MA < 1 (di < do)

What if the mechanical advantage is less than 1? The output force is smaller than the input force. It seems harder to do the work, but the input distance is shorter.

Mechanical Advantage Think of a broom. The input force is greater than the output force. You apply more effort to the end of the broom than the broom has friction with the floor. BUT how far you move the broom handle is much less than how far the broom moves across the floor.