Figure 5 is a speed limit sign from a European motorway. The speeds shown are in km/h (kilometres per hour). (a) (i) The sign tells drivers to drive at a slower speed in wet weather. Explain why it is safer for drivers to drive at a slower speed in wet weather. (ii) Show that a speed of 31 m/s is less than a speed of 130 km/h. (iii) The driver’s reaction time is the time between the driver seeing an emergency and starting to brake. A car is travelling at a speed of 31 m/s. The car travels 46 m between the driver seeing an emergency and starting to brake. Calculate the driver’s reaction time. Give your answer to 2 significant figures.

GCSE Edexcel Physics Speed: Figure 5 is a speed limit sign f

Figure 5 is a speed limit sign from a European motorway - Edexcel - GCSE Physics - Question 3 - 2022 - Paper 1

Question 3

Figure 5 is a speed limit sign from a European motorway. The speeds shown are in km/h (kilometres per hour). (a) (i) The sign tells drivers to drive at a slower spe... show full transcript

Worked Solution & Example Answer:Figure 5 is a speed limit sign from a European motorway - Edexcel - GCSE Physics - Question 3 - 2022 - Paper 1

Step 1

Explain why it is safer for drivers to drive at a slower speed in wet weather.

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Answer

Driving at a slower speed in wet weather is safer due to the reduced friction between the tyres and the wet road surface. When the road is wet, it becomes slippery, which can lead to a loss of traction and an increased risk of skidding. Additionally, wet conditions can decrease visibility, which may affect the driver's ability to react to hazards. A slower speed also means a longer stopping distance, giving drivers more time to react to any potential emergencies.

Step 2

Show that a speed of 31 m/s is less than a speed of 130 km/h.

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Answer

To demonstrate that 31 m/s is less than 130 km/h, we can convert 31 m/s to kilometers per hour. Since 1 m = 0.001 km, we have:

31 ext{ m/s} = 31 \times 3600 \times 0.001 = 111.6 \text{ km/h}

Now comparing 111.6 km/h with 130 km/h shows that 31 m/s is indeed less than 130 km/h.

Step 3

Calculate the driver’s reaction time.

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Answer

To find the driver's reaction time, we use the formula:

ext{Reaction Time} = \frac{\text{Distance}}{\text{Speed}}

Here, the distance traveled is 46 m and the speed is 31 m/s:

ext{Reaction Time} = \frac{46 ext{ m}}{31 ext{ m/s}} \approx 1.48 ext{ s}

Rounding to 2 significant figures, the driver's reaction time is approximately 1.5 seconds.

Figure 5 is a speed limit sign from a European motorway - Edexcel - GCSE Physics - Question 3 - 2022 - Paper 1

Worked Solution & Example Answer:Figure 5 is a speed limit sign from a European motorway - Edexcel - GCSE Physics - Question 3 - 2022 - Paper 1

Explain why it is safer for drivers to drive at a slower speed in wet weather.

Show that a speed of 31 m/s is less than a speed of 130 km/h.

Calculate the driver’s reaction time.

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