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9 marksWork, Energy & Power

CSEC Physics · May/June 2009 · Paper 2 · Question 4(b)(ii)

The Tour de France is a three-week-long cycling race. Acceleration due to gravity, g = 10 m s⁻².

One particular descent goes from 2100 m to 1600 m. Assuming the work done against friction is 90% of the potential energy change of the cyclist and the cycle, what INCREASE in speed in km/h can a rider attain by the end of the descent?

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Other parts of this question

  1. 4(a)(i)State the law of the conservation of energy.[6 marks]
  2. 4(a)(ii)What is the difference between 'potential energy' and 'kinetic energy'?[6 marks]
  3. 4(a)(iii)Does the fact that heat is lost when work is done against friction violate the law of conservation of energy? Justify your answer.[6 marks]
  4. 4(b)(i)If a cyclist of mass 70 kg uses a bicycle of mass 7 kg, how much work must the cyclist do against gravity in order to ascend to 2100 m from sea level (0 m)?[9 marks]
  5. 4(b)(iii)What is the average rate of energy conversion of the cyclist and cycle if the descent in part (ii) takes 1 minute at constant speed?[9 marks]

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