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 Kinetic Energy: 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 find the kinetic energy (KE), we use the formula:

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

Substituting the given values:

Mass (m) = 68 kg
Velocity (v) = 12 m/s

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

Calculating further:

$KE = \frac{1}{2} \times 68 \times 144 = 4900 \text{ J}$

Therefore, the kinetic energy is 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 uses the brakes to stop, the following energy transfers occur:

The kinetic energy of the cyclist and bicycle is converted into thermal energy due to friction between the brake pads and the wheel.
This thermal energy is dissipated into the surroundings, causing the bicycle to slow down and eventually 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 work-energy principle. The work done (W) is given as 1600 J and the distance (d) is 28 m.

Using the formula:

$W = F \times d$

Rearranging for force (F):

$F = \frac{W}{d} = \frac{1600 ext{ J}}{28 ext{ m}}$

Calculating:

$F = \frac{1600}{28} \approx 57.14 ext{ N}$

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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