Figure 3 shows competitors in the wheelchair race at the London Marathon - AQA - GCSE Physics Combined Science - Question 2 - 2022 - Paper 2

To calculate the average air resistance, we use the work done against air resistance:

$W = F \cdot s$

Given:

• Work done ($W$) = 3 360 000 J
• Distance ($s$) = 42 000 m

We need to rearrange the formula to solve for force ($F$):

$F = \frac{W}{s} = \frac{3 360 000}{42 000} = 80 \, \text{N}$

Thus, the average air resistance is 80 N.

The correct equation that links distance travelled, speed, and time is:

distance travelled = speed × time

We tick this box as our answer.

To calculate the average speed, we use the equation:

$v = \frac{d}{t}$

Given:

• Distance ($d$) = 42 000 m
• Time ($t$) = 5600 s

Substituting the values:

$v = \frac{42 000}{5600} = 7.5 \, \text{m/s}$

Thus, the average speed of the winner is 7.5 m/s.

The speed of a competitor changes during the race for several reasons:

1. Acceleration at the Start: Competitors may start off quickly, leading to an increase in speed.

2. Terrain Variability: The course may include hills and varying surfaces which can cause competitors to speed up or slow down (e.g., faster downhill, slower uphill).

3. Fatigue: As the race progresses, competitors may tire, resulting in a decrease in speed as they exert less force to maintain their pace.

4. Strategic Factors: Competitors may change their speed in response to others' movements during the race, either to maintain or increase their position.

5. Pacing Changes: Some competitors may start strong and then pace themselves through the race, which can lead to fluctuations in their speed.

These factors collectively contribute to the dynamic nature of each competitor's speed throughout the marathon.