A cyclist is riding a bicycle at a steady velocity of 12 m/s - Edexcel - GCSE Physics - Question 3 - 2018 - Paper 1

When the cyclist applies the brakes, the following energy transfers occur:

• The kinetic energy (the energy of motion) of the cyclist and bicycle decreases as they slow down.
• This energy is transferred to thermal energy (heat) in the brakes and the surroundings as friction occurs, causing the brakes to heat up.

To calculate the average force, we can use the formula:

$\text{Force} = \frac{\text{Work}}{\text{Distance}}$

Here, the work done is 1600 J and the distance is 28 m:

$\text{Force} = \frac{1600 \text{ J}}{28 \text{ m}} = 57.14 \text{ N}$

Thus, rounding the answer gives us an average force of approximately 57 N.

The average power can be calculated using the formula:

$\text{Power} = \frac{\text{Energy}}{\text{Time}}$

For session 1:

• Energy = 45.2 kJ = 45200 J and Time = 300 s:

$\text{Power} = \frac{45200 \text{ J}}{300 \text{ s}} = 150.67 \text{ W}$

For session 2:

• Energy = 37.9 kJ = 37900 J and Time = 300 s:

$\text{Power} = \frac{37900 \text{ J}}{300 \text{ s}} = 126.33 \text{ W}$

Thus, the athlete developed more power during session 1 compared to session 2.