1 / 19

Machines and MA

Machines and MA. Page 178-195. Simple machines. Means a machine that only uses the forces directly applied and accomplishes its work with a simple motion. Basic simple machines include gears(wedge) screw, pulleys, wheel and axle, ramp (inclined plane) lever. Simple machines.

gay
Download Presentation

Machines and MA

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Machines and MA Page 178-195

  2. Simple machines • Means a machine that only uses the forces directly applied and accomplishes its work with a simple motion. • Basic simple machines include gears(wedge) screw, pulleys, wheel and axle, ramp (inclined plane) lever

  3. Simple machines • Input force is the force that you apply • Output force is the force that does the action

  4. Mechanical Advantage • MA of a Lever • MAlever = Linput • Loutput • L stands for length

  5. Mechanical Advantage • Of pulleys is due to force of tension • Noted as the amount of ropes • MA = output force • input force

  6. Mechanical Advantage • Input gear is the one you turn or apply forces to • Output gear is connected to the output of the machine • Gear ration is the ratio of output turns to input turns • MA = input torque divided by output torque or the inverse of gear ratio

  7. Mechanical Advantage • MA = distance along the ramp divided by the height of the ramp • Friction causes high MA of ramps to not work

  8. Mechanical Advantage • Screw is a simple machine that turns rotating motion into linear motion • MA = average circumference of the thread divided by the vertical distance is the head of the screw

  9. Work • Always done in a parallel direction • W= fd • W= Fd cosine of the angle • W = mgd or mgh • Input work never equals output work because of friction

  10. Energy • Energy is the ability to make things change. • Work is the action of making things change.

  11. Forms of Energy • Mechanical energy • Light energy • Nuclear energy • Electrical energy • Chemical energy • Thermal energy • Pressure energy

  12. Potential energy • Means that something is capable of becoming active. • Calculate Potential energy or Ep • Ep = mgh • Rate of work = mgh divided by time (s)

  13. Kinetic energy • Energy of motion • Kinetic energy equals Ek • Ek = ½ mv2

  14. Deriving the formula for Ek • Step 1 Work is force times distance, but force is mass times acceleration. The work done on an object is therefore its mass X acceleration X distance. • W =Fd =(ma) X d = mad

  15. Deriving the formula for Ek • 2. The kinetic energy formula involves only mass and speed. In chapter 4 you found a relationship between distance traveled acceleration, and time. • . D = 1/2at2

  16. Deriving the formula for Ek • 3. Replacing distance in the equation for work and combining similar terms creates: • W = ma(1/2at2) = 1/2ma2r2

  17. Deriving the formula for Ek • 4. When an object starts from at rest with constant acceleration, its speed is equal to its acceleration multiplied by the time it has been accelerating. Mathematically, v =at, therefore v2 =a2r2. This is the result that is needed. Replace the a2r2 with v2 and the resulting work is exactly the formula for kinetic energy.

  18. Deriving the formula for Ek • v = at  v2 = a2r2 • W = ½ma2r2  W = ½mv2

  19. Law of conservation of energy • Energy can never be created or destroyed only changed from one form to another

More Related