Simple Machines: Beyond the piano we talked about yesterday.

Mechanical Advantage The ratio of the output and input forces that are used within a machine. MA=effort arm/load arm The effort arm is the distance from the fulcrum to the force used to lift an object. Effort Arm Force

Mechanical Advantage The load arm or resistance arm is the distance from the fulcrum to the object being lifted. Load Arm

Mechanical Advantage Math If the distance from the fulcrum to the person lifting is 1.6 meters, the distance from the fulcrum to the object being lifted is 0.4 meters: MA=1.6/0.4=4 This means that a person can lift something four times heavier than normal

Levers There are three classes of levers:

First Class of Lever The fulcrum is in the middle and the effort arm and resistance arm are on opposite sides. When the force pushes down, the item goes up. The MA is one.

Second Class of Levers The fulcrum is at the end The object (load) is in the middle and the person lifting is at the other end of the lever arm. When the force pulls up, the object goes up. Effort Load Fulcrum

Third Class of Lever The fulcrum is at the end. The person lifting is somewhere in the middle and the object being lifted is at the other end of the fulcrum arm. When the force pulls up, the load goes up. The MA is less than one, but moving the load arm and effort arm closer together increases the MA.

Third Class of Lever

Wheel and Axel A larger wheel connected by a smaller cylinder or axel. The axel is fastened to the wheel so they turn together. The wheel moves a greater distance than the axel but requires less force. The axel moves a shorter distance but requires more force.

Wheel and Axel

Wheel and Axle A wheel and axle is really two machines in one The first part is the wheel, it reduces friction when rolling something Only part of the wheel touched the ground so there is not a lot of friction The bigger the wheel, the easier it is to move it.

Wheel and Axle The larger wheel (on the outside) rotates around the smaller wheel (on the inside). The effort or resistance force can be applied to either wheel. The wheels can have a solid axle in the middle.

Wheel and Axle Because the wheel is larger than the axle, it always moves through a greater distance then the axle. A force applied to the wheel is multiplied when it is transferred to the axle, which travels a shorter distance than the wheel.

Inclined Plane A flat surface, set at an upward angle It has no moving parts Helps overcome larger resistance You use relatively little force to push an object up a distance. The higher the slant the more work is required.

Pulleys Used as a way to use your weight to lift an object The same amount of force must be used, but the direction of the effort force changes

Pulleys Each supporting loop of rope holds half the weight, so only half the effort force is need to lift an object.

Work Work is done when an object is moved in the direction of the applied force. The greater the applied force, the more work is done.

Work Work = force X distance Measured in Newtons There’s Math?!! Work = force X distance Measured in Newtons Distance measured in meters Joules = Newton X meters

Work W=fxd or W=50Nx10m=500J So try this: Using a force of 50 N the teacher pushed a computer cart across to another classroom 10 m away. How much work did the teacher do? W=fxd or W=50Nx10m=500J