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 v^2 (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.

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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.

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Answer

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

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

Where:

m = total mass = 68 kg
v = velocity = 12 m/s

Substituting the values into the equation:

KE = \frac{1}{2} \times 68 \text{ kg} \times (12 \text{ m/s})^2

Calculating:

KE = \frac{1}{2} \times 68 \times 144 = 4896 ext{ J}

Thus, the kinetic energy is 4896 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 brakes to stop, the kinetic energy of the bicycle and cyclist is transformed into thermal energy due to friction between the brake pads and the wheel rim. This thermal energy is dissipated into the surroundings, causing the temperature of the braking system to increase. Additionally, some energy may also be transferred to the air as sound energy, producing noise during the braking process.

Step 3

Calculate the average force the cyclist exerts.

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Answer

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

ext{Work} = ext{Force} \times ext{Distance}

Rearranging this gives us:

ext{Force} = \frac{ ext{Work}}{ ext{Distance}}

Given that the work done = 1600 J and the distance traveled = 28 m, we can substitute these values:

ext{Force} = \frac{1600 ext{ J}}{28 ext{ m}} \approx 57.14 ext{ N}

Thus, the average force the cyclist exerts is approximately 57.14 N.

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Questions answered

A cyclist is riding a bicycle at a steady velocity of 12 m/s - Edexcel - GCSE Physics - Question 9 - 2018 - Paper 1

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

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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