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.

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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 is the mass (68 kg)
v is the velocity (12 m/s)

Substituting the values: $KE = \frac{1}{2} \times 68 \times (12)^2$ $KE = \frac{1}{2} \times 68 \times 144$ $KE = 34 \times 144$ $KE = 4896 \text{ J}$

Thus, the kinetic energy of the cyclist and bicycle 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 uses the brakes to stop, the kinetic energy of the bicycle and cyclist is converted into thermal energy through friction. The brake pads generate heat as they rub against the wheels, dissipating the kinetic energy. This transformation results in a decrease in the system's kinetic energy, which leads to a reduction in speed until the bicycle comes to a stop.

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 formula:

$F = \frac{W}{d}$

Where:

F is the average force
W is the work done (1600 J)
d is the distance traveled (28 m)

Substituting the values: $F = \frac{1600}{28}$ $F \approx 57.14 \text{ N}$

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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