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13 November 2014. Power and electrical power. Keywords : Power, Energy, Weight, Force. Outcomes. All students should be able to describe what makes an object powerful or not. Most students should be able to define power and use the equation.
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13 November 2014 Power and electrical power Keywords: Power, Energy, Weight, Force
Outcomes • All students should be able to describe what makes an object powerful or not. • Most students should be able to define power and use the equation. • Some students should be able to evaluate practical work and describe how to make it more valid and reliable.
Powerful cranes Which is the most powerful crane? Explain why.
work done time taken power = How is power calculated? The power exerted by an object can be calculated using one of two equations: • 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.
work done time power = Calculating power question 1 A lawnmower engine does 10kJ of work in 10 seconds. What is the power of the engine? = 10,000 / 10 = 1,000W = 1kW
work done time energy transfer time power = = Calculating power question 2 A car transfers 12mJ of energy in 2 minutes. What is the power of the car? = 12,000,000 / 120 = 100,000W = 100kW
And finally – we find out – who are more powerful – boys or girls? • Force x distance = energy • Energy/time = power Analysis: What conclusion can you draw? Evaluation: was the evidence reliable? Explain.