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 and bicycle. Use the equation KE = 1/2 x m x v² (b) Describe the energy transfers that happen when the cyclist uses the brakes to stop. (c) The cyclist starts to cycle again. The cyclist does 1600 J of useful work to travel 28 m. Calculate the average force the cyclist exerts.

GCSE Edexcel Physics Combined Science Energy stores & Transfers: A cyclist is riding a bicycle at

A cyclist is riding a bicycle at a steady velocity of 12 m/s - Edexcel - GCSE Physics Combined Science - Question 6 - 2018 - Paper 1

Question 6

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 an... show full transcript

Worked Solution & Example Answer:A cyclist is riding a bicycle at a steady velocity of 12 m/s - Edexcel - GCSE Physics Combined Science - Question 6 - 2018 - Paper 1

Step 1

Calculate the kinetic energy of the cyclist and bicycle.

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Answer

To calculate the kinetic energy (KE) of the cyclist and bicycle, we use the formula:

$KE = \frac{1}{2} \times m \times v^2$

Substituting the known values:

Mass, m = 68 kg
Velocity, v = 12 m/s

Substituting into the formula:

$KE = \frac{1}{2} \times 68 \times 12^2$

Calculating the value: $KE = \frac{1}{2} \times 68 \times 144 = 4896 J$

Therefore, the kinetic energy is approximately 4900 J.

Step 2

Describe the energy transfers that happen when the cyclist uses the brakes to stop.

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Answer

When the cyclist applies the brakes, the kinetic energy of the cyclist and bicycle is transformed mainly into thermal energy due to friction between the brake pads and wheels. This thermal energy is dissipated into the surrounding environment. Additionally, some energy may be sound energy produced from the braking process.

Step 3

Calculate the average force the cyclist exerts.

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Answer

To find the average force exerted by the cyclist, we can use the work-energy principle, which states:

$Work = Force \times Distance$

Rearranging for Force gives: $Force = \frac{Work}{Distance}$

Substituting the known values:

Work = 1600 J
Distance = 28 m

$Force = \frac{1600}{28} \approx 57.14 N$

Thus, the average force the cyclist exerts is approximately 57 N.

A cyclist is riding a bicycle at a steady velocity of 12 m/s - Edexcel - GCSE Physics Combined Science - Question 6 - 2018 - Paper 1

Worked Solution & Example Answer:A cyclist is riding a bicycle at a steady velocity of 12 m/s - Edexcel - GCSE Physics Combined Science - Question 6 - 2018 - Paper 1

Calculate the kinetic energy of the cyclist and bicycle.

Describe the energy transfers that happen when the cyclist uses the brakes to stop.

Calculate the average force the cyclist exerts.

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