Mechanical Advantage You mean I don’t have to use the shovel?!

Last time we discussed the different simple machines: Wheel & Axle Think: Why do we use machines to do work instead of doing it ourselves? work instead of doing it ourselves? Main Concept 5: What we really want to do is get the machine to work “efficiently”. “Efficient” machine to work “efficiently”. “Efficient” basically means to “work really well”.

Mechanical Advantage Ways of making WORK easier to accomplish (less effort): OR Both will get the same work done, but which one takes less effort to accomplish the work? Think: Does more power always mean less effort? Think: In the Work & Power Lab, were the steps with more power easier the steps with more power easier for you to do? (Less or More Effort?) Using a machine allows for more power with less effort from you! This is why we use machines. Main Concept 6: Mechanical Advantage is all about getting the machine to make the job as easy for you as possible!

The equation for M.A. The higher the Mechanical Advantage, the easier it is to move something. Basic M.A.= 1 We want to make the MA number bigger!!! Means more Output from the machine, less Input force from you! = less effort!!! The Big Point: We want machines to do as much work as possible with as little effort from us as we can! Computers continue to Think about this: Computers continue to get easier and easier to use. How have cell phones become easier to use compared to original phones or even early cell phones! Think about this: How have cell phones become easier to use compared to original phones or even early cell phones! = MA

Mechanical Advantage Main Concept 7: Thethe, theit is to accomplish the work. The Higher the Mechanical Advantage, the Easier it is to accomplish the work. Force 5 N = 1 2 N 8 N = 4 We want to make this number bigger = easier to do Notice that when there is more Output than Input force, the MA number increases! What the machine does What you do

Class Inquiry Activities Mechanical Advantage of Inclined Planes (Ramps) Lab Mechanical Advantage of Levers Lab

70 cm 50 cm 30 cm Fulcrum Position (cm) Output Force (N) Input Force (N) Mechanical Advantage Effort 50 cm 5 N1XXXXX 30 cm 5 N More Less 70 cm 5 N More Less M.A. 1 st Class Lever

M.A. 2 nd Class Lever Mass Position (cm) Output Force (N) Input Force (N) Mechanical Advantage Effort 50 cm 5 NXXXXX 30 cm 5 N More Less 70 cm 5 N More Less

M.A. 3 rd Class Lever Input Force Position (cm) Output Force (N)Input Force (N) Mechanical Advantage Effort 50 cm 5 NXXXXXX 30 cm 5 N More Less 70 cm 5 N More Less

Force M. A. of Levers Work = Input Force x Input Distance Work = Output Force x Output Distance Distance Force Distance Don’t forget: Work of Input = Work of Output In this case, with the fulcrum right in the center, the forces, distance and total input/output work are exactly the same! Think: when force and distance are exactly the same; is there any M.A? Think: If the Input and Output are exactly the same is there any point to using a machine?

So how can we increase M.A. of a lever? Force Distance We have to adjust how we set up the machine itself! In this case we can move the fulcrum and change the distance of the output and input: Notice that mathematically, even though the amounts of distance and force have changed the total work done on both sides remains the same! Notice what happens to the force and distance of each side when we move Fulcrum closer to the mass Output: Less distance but more force!Input: More distance but less force! Work = Output Force x Output DistanceWork = Input Force x Input Distance

Class 1 Levers: Notice that the effort arms are different lengths. Longer Input/effort “arms “give the scissors more mechanical advantage. **In other words, it makes it easier to cut stuff! Output/Result Arm Input/Effort Arm Output/Result Arm Input/Effort Arm

Class 2 Lever: If we were to increase the length of the input arms on the wheelbarrow, we would give it more mechanical advantage. In other words, it makes it easier to lift stuff. Mass to be lifted

Class 3 Levers:

M.A. of an Incline Plane: To give this simple machine more mechanical advantage, simply make the ramp longer Notice: Did the height of the ramp change? The same amount of work was accomplished with less force on your part! The ramp is now longer and less steep Distance Work that needs to be accomplished

Input Work (Effort Side) M.A. of Pulleys: Output work side When you use a basic single pulley setup, the M.A. = 1 Force Notice that the force and distance is equal Distance Force In order to get M.A. you need to change the distance of your input pull!

Output (Resultant Side) Input (Effort Side) Movable Pulleys give M.A. Work = Force x Distance Force Distance Pulleys only have mechanical advantage when you use a moveable pulley with your setup. Force When you increase the Input distance, the Input force automatically goes down and the Output force automatically goes up!!! Notice that you have to pull more rope to accomplish the same output distance. This is the point! More Input distance will lessen then amount of Input force needed! Watch the difference in distance for Input and the Output!

Input Force (Effort) Output Force (Result) Pulleys only have mechanical advantage when you use a moveable pulley with your setup. By making a combination of Pulleys, we are adding even more input distance, which should lower out Input force even more = more M.A.!!! Movable + Fixed Pulley Combination (“Block and Tackle”) Moveable Pulley Fixed Pulley