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Understanding Work, Power, and Energy in Everyday Scenarios

This module covers key concepts in physics related to work, power, and energy, illustrated through various examples. Explore a comparison of two individuals, Mike and Joe, examining who did more work and produced more power under differing conditions. The module also discusses electricity bills, clarifying the difference between energy and power. Through practical scenarios involving common appliances like hair dryers and microwaves, learn how energy consumption affects monthly costs. This material is essential for grasping the fundamentals of physical work and energy in real-life contexts.

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Understanding Work, Power, and Energy in Everyday Scenarios

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  1. Module 5, Recitation 2 • Concept Problems, Power

  2. ConcepTest Time for Work I 1)Mike 2) Joe 3) both did the same work Mikeapplied 10 N of force over 3 m in10 seconds. Joeapplied the same force over the same distance in1 minute. Who did more work?

  3. ConcepTest Time for Work I 1)Mike 2) Joe 3) both did the same work Mikeapplied 10 N of force over 3 m in10 seconds. Joeapplied the same force over the same distance in1 minute. Who did more work? Both exerted the same force over the same displacement. Therefore, both did the same amount of work. Time does not matter for determining the work done.

  4. ConcepTestTime for Work II 1) Mike produced more power 2) Joe produced more power 3) both produced the same amount of power Mike performed 5 J of work in 10 secs. Joe did 3 J of work in 5 secs. Who produced the greater power?

  5. ConcepTest Time for Work II 1) Mike produced more power 2) Joe produced more power 3) both produced the same amount of power Mike performed 5 J of work in 10 secs. Joe did 3 J of work in 5 secs. Who produced the greater power? Since power = work / time, we see that Mike produced 0.5 W and Joe produced 0.6 W of power. Thus, even though Mike did more work, he required twice the time to do the work, and therefore his power output was lower.

  6. ConcepTestElectric Bill 1)energy 2) power 3) current 4) voltage 5) none of the above When you pay the electric company by the kilowatt-hour, what are you actually paying for?

  7. ConcepTestElectric Bill (1)energy (2) power (3) current (4) voltage (5) none of the above When you pay the electric company by the kilowatt-hour, what are you actually paying for? We have defined: Power = energy / time So we see that: Energy = power x time This means that the unit of power x time (watt-hour) is a unit of energy !!

  8. ConcepTestEnergy Consumption 1)hair dryer 2) microwave oven 3) both contribute equally 4) depends upon what you cook in the oven 5) depends upon how long each one is on Which contributes more to the cost of your electric bill each month, a 1500-Watt hair dryer or a 600-Watt microwave oven? 600 W 1500 W

  9. ConcepTest Energy Consumption (1)hair dryer (2) microwave oven (3) both contribute equally (4) depends upon what you cook in the oven (5) depends upon how long each one is on Which contributes more to the cost of your electric bill each month, a 1500-Watt hair dryer or a 600-Watt microwave oven? We already saw that what you actually pay for is energy. To find the energy consumption of an appliance, you must know more than just the power rating — you have to know how long it was running. 600 W 1500 W

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