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Energy:

Definitions:. Energy:. Ability to do work. Work= . Force x Distance. Force:. A Push or a Pull. What is work?. In science, the word work has a different meaning than you may be familiar with.

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Energy:

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  1. Definitions: Energy: Ability to do work Work= Force x Distance Force: A Push or a Pull

  2. What is work? • In science, the word work has a different meaning than you may be familiar with. • The scientific definition of work is: using a force to move an object a distance (when both the force and the motion of the object are in the same direction.)

  3. Work or Not? • According to the scientific definition, what is work and what is not? • a student carrying a book bag • a mouse pushing a piece of cheese with its nose across the floor

  4. What’s work? • A scientist delivers a speech to an audience of his peers. No • A body builder lifts 350 pounds above his head. Yes • A father carries her baby from room to room. No • A mother pushes a baby in a carriage. Yes • A teenager carries a 20 km grocery bag to the car? No

  5. What are simple machines? • Simple machines are elementary devices (including levers and pulleys) that provide mechanicaladvantage.

  6. Formula for work Work = Force x Distance • The unit of force is newtons • The unit of distance is meters • The unit of work is newton-meters • One newton-meter is equal to one joule • So, the unit of work is a joule

  7. Work Equation • Work (joules) = force (newtons) X distance ( meters) • W=Fd A painter lifts a can of paint that weighs 40 N a distance of 2 m. How much work does she do?

  8. TFSA Method • T= Title • What operation are you completing? What are you looking for? • F = Formula • What is the formula used to complete the operation? • S = Substitution • This is where you actually plug in the numbers • A = Answer

  9. A painter lifts a can of paint that weighs 40 N a distance of 2 m. How much work does she do? • T= Title How much work does she do? • F = Formula Work = force X distance • S = Substitution force: f = 40 newtons distance: d = 2 m Work = (40n)(2m)

  10. A = Anwser 80 (N)(M) 80 Joules Work = 80 Joules

  11. Work Equation • Work (joules) = force (newtons) X distance ( meters) • W=Fd A painter lifts a can of paint that weighs 40 N a distance of 2 m. How much work does she do?

  12. If you push a lawn mower, the horizontal force is 300 N. If you push the mower a distance of 500 m, how much work do you do? • Title: How much work do you do? • Formula: Work = Force X Distance • Substitute: W =(300n)(500m) • Answer: W = 150,000 newtons meters W = 150,000 Joules

  13. Take a Closer Look at theSix Simple Machines

  14. Simple Machines all have one thing in common: • They give their users some form of advantage. They do 3 useful things: • multiply effort • multiply distance • change direction of force

  15. Definition: Mechanical Advantage is a ratio of the load or resistance to the effort or force.

  16. Lift and push objects • put pressure on objects • hold or break objects The weight lifted, or the resistance overcome, is the LOAD. Simple Machines Can:

  17. Definitions: Load is the weight or resistance that is moved using a simple machine. Resistance is an opposing force tending to prevent motion. Effort is the force applied to move a load using a simple machine. Force is a push or a pull. Fulcrum is the point at which a lever arm picots.

  18. Water in a hole to deep to reach with a bucket A boulder too massive to push, role or lift

  19. Six Simple Machines • They give their users some form of advantage. They do 3 useful things: • multiply effort • multiply distance • change direction of force

  20. LEVER Activity A lever is a tool that people use to make work easier. Levers are used to lift things or to overcome resistance. Levers give us an advantage by making work easier. A lever arm is a stick or beam free to pivot at a point. The fulcrum is the point around which the leve arm pivots.

  21. Rules for the Spring Scale Newtons is the unit used to measure force in the metric system. 1.) Always zero the scales before starting the day’s activity. 2.) Always use the scale right side up, never upside down. 3.) Pull until the lever arm is level, then read the effort. This works best if one student pulls the scale while the another reads the effort. 4.) Stop before the scale goes past the 10-N limit.

  22. Inclined Planes • An inclined plane is a flat surface that is higher on one end • Inclined planes make the work of moving things easier

  23. Inclined Plane • The Egyptians used simple machines to build the pyramids. One method was to build a very long incline out of dirt that rose upward to the top of the pyramid very gently. The blocks of stone were placed on large logs (another type of simple machine - the wheel and axle) and pushed slowly up the long, gentle inclined plane to the top of the pyramid.

  24. Screw The screw is an inclined plane wound around a central cylinder. The mechanical advantage of an screw can be calculated by dividing the circumference by the pitch of the screw. Pitch equals 1/ number of turns per inch.

  25. Wedges • Two inclined planes joined back to back. • Wedges are used to split things.

  26. WHEEL AND AXEL • Wheel and axel are two different-sized wheels that turn together around the same point. A ferris wheel is an example of a wheel and axle.

  27. Pulleys • Pulley are wheels and axles with a groove around the outside • A pulley needs a rope, chain or belt around the groove to make it do work

  28. First Class Lever A Class-1 lever has the fulcrum located somewhere between the effort and the load.E = EffortF = FulcrumL = Load

  29. First Class Lever . • Common examples of first-class levers include crowbars, scissors, pliers, tin snips and seesaws.

  30. Second ClassLever A Class-2 lever has the fulcrum located at one end of a lever arm. The Load is between the fulcrum and the effort has not changed.F = FulcrumL = LoadE = Effort

  31. Second Class Lever • Examples of second-class levers include nut crackers, wheel barrows, doors, and bottle openers.

  32. Third Class Lever A Class-3 lever the fulcrum is at one end, and the effort is applied between the fulcrum and the load. The direction of effort is not changed. F = FulcrumE = EffortL = Load

  33. Third Class Lever • Examples of third-class levers include tweezers, broom, hammers, and shovels.

  34. Work and Power – Section 1 – Page 76 If you push a lawn mower, the horizontal force is 300 N. If you push the mower a distance of 500 m, how much work do you do?

  35. Work and Power – Section 1 – Page 76 If you push a lawn mower, the horizontal force is 300 N. If you push the mower a distance of 500 m, how much work do you do? • Title: How much work do you do? • Formula: Work = Force X Distance • Substitute: W =(300n)(500m) • Answer: W = 150,000 newtons meters W = 150,000 Joules

  36. Work and Power – Section 1 – Page 77 In the course of a short race, a car does 50,000 Joules of work in 7 seconds. What is the power of the car during the race?

  37. Work and Power – Section 1 – Page 77 In the course of a short race, a car does 50,000 Joules of work in 7 seconds. What is the power of the car during the race? • Title: What is the power of the car during the race? • Formula: Power = Work / Seconds • Substitute: P =50,000 J / 7 S • Answer: P = 7,142.86 WATT

  38. Work and Power –Sec 1Pg 78 • Describe a situation in which work is done on an object. • Evaluate which of the following situation involves more power: 200 J of work done in 20 s or 50 j of work done in 4 s? Explain

  39. 200 J of work done in 20 s or 50 J of work done in 4 s? • Title: What is the power? • Formula: Power = Work / Seconds • Substitute: P =200 J / 20 S • Answer: P = 10 WATTs OR • Title: What is the power? • Formula: Power = Work / Seconds • Substitute: P = 50 J / 4 S • Answer: P = 12.5 WATTs

  40. Work and Power –Sec 1Pg 78 3. Determine two ways power can be increased. • Calculate how much power, in watts, is needed to cut a lawn in 50 minutes if the work involved is 100,000 Joules.

  41. Calculate how much power, in watts, is needed to cut a lawn in 50 minutes if the work involved is 100,000 Joules. • Title: What is the power needed? • Formula: Power = Work / Seconds • Substitute: P =100,000 J / 3,000 S • Answer: P = 33.33 WATTs

  42. Work and Power –Sec 1Pg 78 • Think Critically: Suppose you are pulling a wagon with the handle at an angle. How can you make your task easier?

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