Work Done and Power (GCSE Physics)

Work Done and Power

Power

Calculating Power

We can calculate a value for power using two different formulas. We previously looked at how to calculate power using work done. Here is a quick recap of what we learnt.

Work Done

Work Done and Power
Work Done and Power

Where:

  • power, P, in watts, W
  • time, t, in seconds, s
  • work done, W, in joules, J

Question: A hair dryer does 45,000J of work in one minute. What is the power rating of the hairdryer?

  1. Write out the appropriate equation.
    In this situation, the appropriate equation is:

Work Done and Power
Work Done and Power
  • Substitute in the numbers.
    Simply put the numbers into our equation.

  • Work Done and Power
    Work Done and Power

    Question: What is the power of a car engine that does 4500J of work in 1.5 minutes?

    1. Write out the appropriate equation.
      In this situation, the appropriate equation is:

    Work Done and Power
    Work Done and Power
  • Work out the value for time.
    In the question, we have been given a value for time in minutes. The equation requires us to give the time in seconds, so we need to convert.

  • Work Done and Power
    Work Done and Power
  • Substitute in the numbers.
    Now that we have the correct values, we can put the numbers into our equation.

  • Work Done and Power
    Work Done and Power

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