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# Work

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### Transcript

• 1. Work and Simple Machines
• 2. Simple Machines
• The six simple machines are:
• Lever
• Wheel and Axle
• Pulley
• Inclined Plane
• Wedge
• Screw
• 3. Simple Machines
• A machine is a device that helps make work easier by
• transferring a force from one place to another
• changing the direction of a force increasing the size of a force
• increasing the distance or speed of a force.
• input force (the force you apply) and the output force (force which is applied to the task).
• When a machine takes a small input force and increases the magnitude of the output force, a mechanical advantage has been produced.
• 5. The Lever
• A lever is a rigid bar that rotates around a fixed point called the fulcrum.
• 6. The 3 Classes of Levers
• determined by:
• location of the effort
• compared to the
• fulcrum.
• 7. The workman uses a trolley to move the large packing case. The fulcrum is the wheel. First Class Lever
• In a first-class lever the fulcrum is located at some point between the effort and resistance forces.
• Common examples of first-class levers include crowbars, scissors, pliers, tin snips and seesaws.
• 8. Second Class Lever The gardener uses a wheel barrow to lift tools and garden waste. The load is in the centre of the barrow With a second-class lever, the load is located between the fulcrum and the effort force. Common examples of second-class levers include nut crackers, wheel barrows, doors, and bottle openers.
• 9. Third Class Lever The fisherman catches the fish which becomes the load at the end of the lever.
• With a third-class lever, the effort force is applied between the fulcrum and the resistance force.
• Examples of third-class levers include tweezers, hammers, and shovels.
• 10. Wheel and Axle
• consist of a large wheel connected to a shaft called an axle.
• When either the wheel or axle turns, the other part also turns.
• 11. Pulley
• A pulley consists of a grooved wheel that turns freely in a frame called a block.
• A fixed pulley does not rise or fall with the load being moved.
• A moveable pulley rises and falls with the load that is being moved.
• 12. Inclined Plane
• An inclined plane is ramp The inclined plane makes it easier to move a weight from a lower to higher elevation.
• 13. Wedge
• The wedge is a modification of the inclined plane. Wedges are used as either separating or holding devices.
• 14. Screw
• Think of the threads of the screw as a type of circular ramp (or inclined plane).
• 15. Whatâ€™s work?
• A scientist delivers a speech to an audience of his peers.
• A body builder lifts 350 pounds above his head.
• A mother carries her baby from room to room.
• A father pushes a baby in a carriage.
• A woman carries a 20 kg grocery bag to her car?
• 16. 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
• 17. Work or Not?
• According to the scientific definition, what is work and what is not?
• a teacher lecturing to a class
• a mouse pushing a piece of cheese with its nose across the floor
• 18. Whatâ€™s work?
• A scientist delivers a speech to an audience of his peers.
• A body builder lifts 350 pounds above his head.
• A mother carries her baby from room to room.
• A father pushes a baby in a carriage.
• A woman carries a 20 kg grocery bag to her car?
• 19. Whatâ€™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 mother carries her baby from room to room. No
• A father pushes a baby in a carriage. Yes
• A woman carries a 20 km grocery bag to her car? No
• 20. Formula for work
• Work = Force x Distance
• The unit of work is a joule
• 21. W=FD
• Work = Force x Distance
• Calculate: If a man pushes a concrete block 10 meters with a force of 20 N, how much work has he done?
• 22. W=FD
• Work = Force x Distance
• Calculate: If a man pushes a concrete block 10 meters with a force of 20 N, how much work has he done? 200 joules
• (W = 20N x 10m)
• 23. Power
• Power is the rate at which work is done.
• Power = Work * /Time
• * (force x distance)
• The unit of power is the watt.