# Forces - Weebly

SIMPLE MACHINES LEVERS 7.5 LEARNING OUTCOMES Define effort, load, fulcrum and simple machines Describe and give a diagram of the three types of levers (1st, 2nd and 3rd class levers) and give examples of each

Calculate mechanical advantage o Machines make it easier to do work over a longer period of time o A simple machine can make a task easier in three different ways. It can: Simp

le change the size of a force Machine s make things speed up

change the direction of a force. o An effective machine is one that reduces the amount of effort (force) required KEY WORDS o Effort is the force applied to a lever to overcome the load or get

a job done. o Load what is lifted or moved by a simple machine. The force actually required to do the job. o Fulcrum is the pivot point/balance/turning point of a lever

1ST CLASS LEVERS o Leavers increase the size of the effort that you can apply or reduce the effort need to get a job done o First class levers The fulcrum is between the load and the effort. 1ST CLASS LEVERS

2ND CLASS LEVERS Second class levers The load is between the effort and the fulcrum 2ND CLASS LEVERS 3RD CLASS LEVERS Third class levers The effort is between the load and

the fulcrum. 3RD CLASS LEVERS SUMMARY QUESTION State the class of lever

acting in each situation CALCULATING MECHANICAL ADVANTAGE A simple machine is a device that uses leverage to magnify force. In other words, they make doing work easier. The efficiency of these machines is determined by calculating their mechanical advantage. Mechanical advantage is a measure of the force amplification attained

by the machine or how much easier does the machine make the work? Mechanical advantage = output force input

force EXAMPLE CALCULATION Calculate the mechanical advantage of a crowbar that requires a force of 60N to shift a 180N rock 180N rock crowbar that requires a force of 60N

Mechanical advantage = 180 N 60N =

3 EXAMPLE CALCULATION Calculate the mechanical advantage of a machine that requires an effort force of 150N to lift a 750N fridge 750N fridge effort force of 150N

Mechanical advantage = 750 N 150 N

= 5

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