Machines and Work I Using Machines A Machines

I. Using Machines A. Machines 1. Machines- devices that make work easier to do

B. How Machines Work 1. Effort Force- The force applied TO the machine 2.

C. Machines multiply your effort 1. Works because less force is applied over larger

II. Types of Simple Machines A. Lever- A bar that is free to pivot

4. Types of Levers: a. 1 st class levers- When the fulcrum is between

B. Pulleys: Fixed and Movable 1. Fixed Pulleys- A pulley attached to a nonmoving

3. Mechanical Advantage a. Determined by the number of ropes supporting upward movement of

C. Wheel and Axle 1. Effort force is applied to the larger wheel 2.

D. Inclined Plane 1. Helps moving an object by decreasing force needed to lift

E. A Screw 1. An inclined plane wrapped around a post 2. Threads help

F. Wedge 1. Wedge- a moving inclined plane 2. Material stays in place while

III. Using Machines A. Compound Machine- 2 or more simple machines used together B.

C. Calculating Work and Power 1. Work = Force x Distance (W=Fxd) a. Unit

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Machines and Work

I. Using Machines A. Machines 1. Machines- devices that make work easier to do 2. Simple Machine- device that does work with one motion a. Used to overcome gravity and friction

B. How Machines Work 1. Effort Force- The force applied TO the machine 2. Resistance Force- The force applied BY the machine to overcome resistance a. Fe x De = Fr x Dr (D- distance) (N x m) b. Effort distance will be larger than the resistance distance c. Resistance force will be larger than the effort force

C. Machines multiply your effort 1. Works because less force is applied over larger distances 2. Mechanical Advantage (MA) - The multiplication of your effort force by a machine

II. Types of Simple Machines A. Lever- A bar that is free to pivot or turn on a fixed point 1. Fulcrum- The fixed point of a lever 2. Effort arm is the arm you apply the force to 3. Resistance arm is the arm applying force to the object a. Mechanical Advantage = Effort arm length / resistance arm length (MA = Le/Lr)

4. Types of Levers: a. 1 st class levers- When the fulcrum is between the effort arm and the resistance arm i. Examples include- scissors and seesaws b. 2 nd class levers- When the resistance is between the effort arm and the fulcrum i. Examples include- wheel barrow and car doors c. 3 rd class levers- When effort arm is between the resistance and the fulcrum i. Examples include- a broom and kicking a soccer ball

B. Pulleys: Fixed and Movable 1. Fixed Pulleys- A pulley attached to a nonmoving object a. Does not multiply force 2. Moveable pulley- attached to a movable object a. Is able to multiply effort b. Effort length must be at least double the resistance length

3. Mechanical Advantage a. Determined by the number of ropes supporting upward movement of the resistance force b. Block and Tackle- Made up of fixed and moveable pulleys

C. Wheel and Axle 1. Effort force is applied to the larger wheel 2. Resistance force is applied to the smaller wheel, the axle 3. Mechanical Advantage a. MA = radius of large wheel/ radius of axle

D. Inclined Plane 1. Helps moving an object by decreasing force needed to lift an object 2. Trade off is, object has to be moved farther 3. MA = Length of slope/ height of slope (MA= Ls/Hs) 4. Examples include ramps and stairs

E. A Screw 1. An inclined plane wrapped around a post 2. Threads help sink screw into wood

F. Wedge 1. Wedge- a moving inclined plane 2. Material stays in place while the wedge moves through it 3. Examples: knives, chisels, and axes

III. Using Machines A. Compound Machine- 2 or more simple machines used together B. Efficiency- how much input work is changed to useful work on the machine 1. Increase efficiency by reducing friction

C. Calculating Work and Power 1. Work = Force x Distance (W=Fxd) a. Unit is Newton meters (Nxm) 2. Power- The rate at which work is done a. Power = Work divided by time (P=W/t) b. Unit is watt = 1 joule per second c. Most appliances are rated in watts