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Levers Information Class 1 lever This class has the fulcrum between the effort and the load. Class 2 levers These levers have the load between the fulcrum and the effort. Class 3 levers Class 3 levers have the effort between the fulcrum and the load. Mechanical Advantage When engineers design machines they need some way of predicting how the machines will work. One way is to compare the size of the effort and the load and you can use very simple mathematics to do this. When you compare the size of the effort and the load it is called the mechanical advantage. The lever is used to explain the idea of mechanical advantage. Mechanical advantage We use machines to allow us to change a small force at the effort into a larger force to move the load. When we compare the sizes of the effort and the load we are talking about the mechanical advantage. We use the abbreviation MA for mechanical advantage and some very simple mathematics to help us find the MA. MA = Load ÷ Effort If the machine uses a small effort to move a much larger load it is said to have a good mechanical advantage. Example An effort of 10N is used to move a load of 50N. What is the MA of this lever? MA = Load ÷ Effort = 50 ÷ 10 =5 The mechanical advantage of the lever is 5. This means that whatever the size of the effort you use it will move a load 5 times larger. There are no units for mechanical advantage; it is just a number. Velocity Ratio When engineers design machines they need some way of predicting how the machines will work. They can use very simple mathematics to help them design the best machine. One way is to use what is called the velocity ratio. The lever is used to explain the idea of velocity ratio. Velocity ratio You need to understand velocity and distance before you can understand the idea of velocity ratio. A ratio is when we compare two similar things. To find the velocity ratio we compare the distances the effort and load move in the same time. We use the abbreviation VR for velocity ratio and simple mathematics will give us the answer. VR = Distance effort moves ÷ Distance load moves Example If the effort moves 5 metres while the load moves 1 metre, what is the velocity ratio? VR = Distance effort moves ÷ Distance load moves =5÷1 =5 The velocity ratio of the lever is 5. This means that whatever distance the load moves the effort must moves 5 times that distance. There are no units for velocity ratio it is just a number. Velocity While speed of a moving body is important in technology there is another word that is even more important and it is velocity. To describe velocity you have to give the speed and the direction in which the body is moving.