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Warm Up 9/25

List the following letters in order from most GPE to lowest KE. Warm Up 9/25. What is work?. What happens when a rocket is launched into space?. When the rocket’s engines are fired, chemical energy in the fuel is transferred to kinetic energy in the rocket.

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Warm Up 9/25

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  1. List the following letters in order from most GPE to lowest KE. Warm Up 9/25

  2. What is work? What happens when a rocket is launched into space? When the rocket’s engines are fired, chemical energy in the fuel is transferred to kinetic energy in the rocket. This transfer of energy is called work.

  3. Work and energy work done = energy transferred What is the link between work and energy? This means the units for work are the same as the units for energy – joules. For example, if a person does 500J of work, then 500J of energy is transferred. In the same way, if a person transfers 250J of energy, then 250J of work is done.

  4. What factors affect work done?

  5. work done = force x distance moved How is work calculated? The work done on an object can be calculated using this equation: • Force is measured in newtons (N). • Distance moved is measured in meters (m). • Work done is measured in joules (j).

  6. work done = force x distance Calculating work done question 1 A cyclist peddles a bicycle with a force of 1,000N moving it 250m. How much work has been done by the cyclist? = 1,000 x 250 = 250,000J = 250kJ

  7. work done force distance = Calculating work done question 2 A truck engine moves a truck with a force of 10kN and does 500kJ of work. How far has the truck traveled? work done = force x distance = 500,000 / 10,000 = 50m

  8. What is Power? Power is the rate at which work is done. A more powerful engine, therefore, does work (i.e. transfers energy) faster than a less powerful engine. Both these planes are about the same mass, but the jet has more powerful engines. This means that chemical energy in the fuel can be transferred to kinetic energy faster, so it will have greater acceleration and a higher top speed.

  9. work done time taken power = How is power calculated? The power exerted by an object can be calculated using the following equation: • Work done is measured in joules (J). • Time is measured in seconds (s). • Power is measured in watts (W). Remember that work done = energy transferred.

  10. work done time power = Calculating power question 1 A lawnmower engine does 10,000J of work in 10 seconds. What is the power of the engine? = 10,000 / 10 = 1,000W

  11. work done time energy transfer time power = = Calculating power question 2 A car transfers 1.2 x 107 J of energy in 2 minutes. What is the power of the car? = 12,000,000 / 120 = 100,000W = 100kW

  12. http://www.youtube.com/watch?v=5EsMmdaYClQ Work and Power Song

  13. More power! What advantages and disadvantages are there in using a more powerful machine?

  14. Powerful cranes

  15. Work, force and distance calculations

  16. Factors affecting work done

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