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A cyclist is riding a bicycle at a steady velocity of 12 m/s - Edexcel - GCSE Physics - Question 9 - 2018 - Paper 1
Question 9
A cyclist is riding a bicycle at a steady velocity of 12 m/s. The cyclist and bicycle have a total mass of 68 kg. (a) Calculate the kinetic energy of the cyclist a... show full transcript
Worked Solution & Example Answer:A cyclist is riding a bicycle at a steady velocity of 12 m/s - Edexcel - GCSE Physics - Question 9 - 2018 - Paper 1
Step 1
Calculate the kinetic energy of the cyclist and bicycle.
Answer
To calculate the kinetic energy (KE) of the cyclist and bicycle, we can use the formula:
Where:
- m = mass of the cyclist and bicycle = 68 kg
- v = velocity = 12 m/s
Substituting the values:
Calculating:
- Calculate ( 12^2 = 144 )
- Multiply by 68: ( 68 \times 144 = 9792 )
- Divide by 2: ( \frac{9792}{2} = 4896 )
Thus, the kinetic energy is ( 4896 , J ).
Step 2
Describe the energy transfers that happen when the cyclist uses the brakes to stop.
Answer
When the cyclist uses the brakes to stop, the kinetic energy of the bicycle is converted into thermal energy due to friction between the brake pads and the wheels. This energy transfer results in the brakes heating up, as the kinetic energy is dissipated as heat. Additionally, some energy may be transferred to the surrounding air as sound energy, noticeable in the form of noise from the braking process.
Step 3
Calculate the average force the cyclist exerts.
Answer
To find the average force exerted by the cyclist, we use the work-energy principle, which states:
Rearranging this formula gives:
Given:
- Work = 1600 J
- Distance = 28 m
Substituting the values:
Thus, the average force the cyclist exerts is approximately ( 57.14 , N ).