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Work and Machines

Learn about work as the transfer of energy through forces moving objects. Explore how machines make work easier by increasing force or distance, and understand effort and resistance forces. Discover the concept of efficiency in machines.

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Work and Machines

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  1. Work and Machines Work: is the transfer of energy that occurs when a force makes an object move For work to be done, a force must make something move ex: pushing on something that doesn’t move is not doing work

  2. Two conditions have to be met to do work on an object • 1. object has to move • 2. motion of the object must be in same direction as force applied When work is done, a transfer of energy always occurs So: Energy is also the ability to do work (not just the ability to cause change)

  3. Calculating Work • Work = force X distance • OR • W = F X d • *Units for work are Joules • (Practice Calculating Work)

  4. Using Machines • Machines: a device that makes doing work easier • Machines increase the force applied to an object OR increase the distance over which a force can be applied Machines can also change the direction of an applied force Ex: car jacks, ramps, wedges

  5. Effort and Resistance Forces • Two forces are involved when a machine is used to do work • Effort force: the force applied to the machine • Resistance force: the force applied by the machine to overcome resistance • Ex: when you pull a nail out w/a hammer, effort force is applied to the handle, resistance force is applied to the nail by the claw

  6. Efficiency: a measure of how much of the work put into a machine is changed into useful output work by the machine • High efficiency means less heat produced from friction • Efficiency = W output/W input X 100% • Friction causes output work to always be less than the input work • SO: Efficiency of a real machine is always less than 100%

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